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Biomedical subjects

J J Smith

Publications and source records attributed to J J Smith.

At least 145 records · Page 8Linked to original sources
PubMed1994

Hemodynamic response to the upright posture.

The authors' objective was to review previous studies of immediate (first 30 seconds) and stabilized (30 seconds to 20 minutes) hemodynamic responses of healthy adults to the head-up posture, with particular reference to alteration of such responses in the elderly and the usefulness of such data in the diagnosis of orthostatic hypotension. The immediate response in healthy young adults is characterized by a prompt rise in heart rate, which peaks at about 8 to 15 seconds and then tapers; the arterial pressure and total vascular resistance decrease sharply at 5 to 10 seconds, followed by a rapid rebound and overshoot. Over the first 30 seconds there is a steady parallel decline of thoracic blood volume and stroke volume; there is also an initial surge of cardiac output followed by a steady decrease. During the stabilized response (30 seconds to 20 minutes), the hemodynamic variables are relatively steady, showing average increases in heart rate of about 15 to 30%, in diastolic pressure of 10 to 15%, and in total vascular resistance of 30 to 40%; during the 5th to 20th minutes there are also decreases in thoracic blood volume averaging about 25 to 30%, in cardiac output 15 to 30%, and in pulse pressure about 5 to 10%. It is evident that in normal human subjects, assumption of the upright posture results in profound hemodynamic changes, most of them occurring during the first 30 seconds. In elderly subjects (aged 60-69 years), there are, in the upright posture, lesser increments of heart rate and diastolic pressure, but no significant differences from younger age groups in the response of thoracic blood volume, cardiac output or total vascular resistance. However, beginning at about age 75, there is an increasing incidence of orthostatic hypotension, which averages about 14 to 20% at age 75 and older. The tendency toward orthostatic hypotension in the elderly is due (1) to the structural and functional changes in the circulation itself, (2) to a decline in autonomic function, and (3) to a probable functional deficiency of the skeletal muscle pump. The authors believe that closer hemodynamic monitoring of orthostatic hypotension patients would considerably increase our understanding and aid in the diagnosis of this condition.

Adult↗
PubMed1994

Method for establishing and measuring in vivo forces in an anterior cruciate ligament composite graft: response to differing levels of load sharing in a goat model.

In order to determine the appropriate load history for optimal remodeling of an anterior cruciate ligament graft, methods for establishing and measuring the graft force due to an external load could be set to a preselected value in in vivo are required. Our objectives with this study were to (a) develop a method in which the graft force due to an external load could be set to a preselected value in a living animal, (b) show that this force could be maintained after fixation, and (c) determine what happens to the forces after the animal has functioned for as long as 2 weeks postoperatively, when differing levels of load sharing between the segments had been set at surgery. The anterior cruciate ligament was reconstructed in 12 goats with use of a bone-patellar tendon-bone graft and a synthetic augmentation device. The forces in the graft segments were established, at the time of surgical fixation, with use of a force-setting technique. In five animals, the tendon segment was set to carry 90% of the total graft force; in the remaining seven animals, the augmentation segment was set to share 90% of the total graft force. Graft forces were measured, with the use of buckle transducers mounted extra-articularly over the anterior tibia, under a 67 N anterior tibial load at 60 degrees of knee flexion before and after fixation and at 2 weeks postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Characterization of random amplified polymorphic DNA (RAPD) products from Xanthomonas campestris and some comments on the use of RAPD products in phylogenetic analysis.

As part of our research to determine phylogenetic relationships of organisms within the phytobacterial species Xanthomonas campestris, we have examined the use of the random amplified polymorphic DNA (RAPD) technique. The objective of this aspect of our research was to determine if a valid cladistic character analysis could be carried out by direct comparison of RAPD products separated on ethidium bromide-stained agarose gels. RAPD products were amplified from 47 Xanthomonas campestris DNA templates using a single oligonucleotide primer. These RAPD products were compared and variation was characterized by Southern analysis of both RAPD products and genomic DNA of the 47 bacterial strains using two cloned RAPD products as probes. Analysis of the data set revealed that the RAPD products were not necessarily homologous or independent, crucial prerequisites for characters to be analyzed in a cladistic phylogenetic analysis. It has been commonly assumed that RAPD variation occurs due to insertion/deletion events or alterations in the primer binding site. Within our data set, we demonstrate absence phenotypes arising from the apparent absence of corresponding loci and also due to the preferred synthesis of alternative RAPD products from unrelated loci. These different types of variation are a reflection of different types of genotypic variation, and direct examination of RAPD products did not allow us to distinguish by which mechanism a particular absence phenotype arose. Although this may not be important for phenetic analyses, for analyses of homologous characters using a cladistic approach it is critical. We also detected unrelated, co-migrating RAPD products and multiple related RAPD products within reaction mixtures. These could both contribute to errors in estimates of similarity, important in any phylogenetic analysis. All of these characteristics of RAPD products should be taken into consideration when RAPD products are used for phylogenetic comparisons.

Blotting, Southern↗
PubMed1994

Mouse pancreatic acinar/ductular tissue gives rise to epithelial cultures that are morphologically, biochemically, and functionally indistinguishable from interlobular duct cell cultures.

Most of the pancreatic exocrine epithelium consists of acinar and intralobular duct (ductular) cells, with the balance consisting of interlobular and main duct cells. Fragments of mouse acinar/ductular epithelium can be isolated by partial digestion with collagenase and purified by Ficoll density gradient centrifugation. We investigated whether previously developed culture conditions used for duct epithelium would result in the selective survival and proliferation of ductular cells from the acinar/ductular fragments. The fragments were cultured on nitrocellulose filters coated with extracellular matrix. After 2 to 4 wk the filters were covered with proliferating cells resembling parallel cultures of duct epithelium by the following criteria: protein/DNA ratio, light and electron microscopic appearance, the presence of duct markers (carbonic anhydrase [CA] activity, CA II mRNA, the cystic fibrosis transmembrane conductance regulator), the near absence of acinar cell markers (amylase and chymotrypsin), a similar polypeptide profile after sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the presence of spontaneous and secretin-stimulated electrogenic ion transport. Both duct and ductular epithelia formed fluid-filled cysts in collagen gels and both could be subcultured. We conclude that acinar/ductular tissue gives rise to ductular cells in culture by some combination of acinar cell death and/or transdifferentiation to a ductular phenotype, accompanied by proliferation of these cells and preexisting ductular cells. These cultures may be used to investigate the properties of this part of the pancreatic duct system, from which most of the pancreatic juice water and electrolytes probably originates.

Amylases↗
PubMed1994

The yield of a second screening flexible sigmoidoscopy in average-risk persons after one negative examination.

BACKGROUND/AIMS: The American Cancer Society recommends that asymptomatic persons aged > or = 50 years undergo sigmoidoscopy every 3-5 years. However, the yield of a second examination 3 years later in persons who are initially negative is unknown. The aim of this study was to determine the yield of a second flexible sigmoidoscopy in average-risk persons aged > or = 50 years after an initial negative examination. METHODS: Two hundred fifty-nine asymptomatic, average-risk persons who had undergone a negative screening flexible sigmoidoscopy examination at age > or = 50 years underwent a second examination at least 2 years later (mean, 3.4 years). RESULTS: The second examination found adenomas in 15 (6%) screenees, but no cancers or large (> 1 cm) or severely dysplastic adenomas were detected. Persons aged > or = 60 years at the time of the second examination were more likely (10%) to have adenomas than those < 60 years (3%) (odds ratio, 3.76; 95% confidence interval, 1.17-12.2), but no advanced lesions were found in persons aged > or = 60 years. CONCLUSIONS: These data suggest that the American Cancer Society should consider changing its recommendation for screening flexible sigmoidoscopy in asymptomatic, average-risk persons to 5-year intervals after a negative examination.

Adenoma↗
PubMed1994

Multiple retroperitoneal schwannomas: case report and review of the literature.

We report a rare case of multiple retroperitoneal schwannomas, initially believed to be an adrenal carcinoma with metastasis. These benign tumors were discovered in a patient presenting with vague back pain. Preoperative radiographic and endocrine evaluations suggested a nonfunctioning adrenal tumor. The final diagnosis and its juxta-adrenal origin were confirmed by histological and immunohistochemical studies. A review of the literature on retroperitoneal schwannoma is included.

Humans↗
PubMed1994

Distribution of injected dexamethasone from the buccal vestibule of the rat mandible.

Thirty-six Sprague-Dawley rats were divided into three groups of 12. Group 1 was a control, whereas group 2 had the dental pulp of the first mandibular molar acutely exposed, and group 3 had dental pulp exposure for 10 days. All animals were injected with 125I-labeled dexamethasone phosphate into the right mandibular vestibule. Each group of 12 was divided into subgroups of 4 and sacrificed at 1, 2, or 4 h. The soft tissue on the buccal side and the mandible with the molars were collected and the radioactivity determined. Dexamethasone was absorbed from the injection site and distributed to the ipsilateral mandible and to the contralateral muscle and bone similarly, regardless of the treatment. Results also indicate a possible osseous affinity for this steroid, which could be beneficial in relieving the pain of intraosseous endodontic flare-ups.

Administration, Buccal↗
PubMed1994

Survival, physiological response and recovery of enteric bacteria exposed to a polar marine environment.

Survival, sublethal injury, and recoverability of Escherichia coli, Enterococcus faecalis, Salmonella typhimurium, and Yersinia enterocolitica were investigated by using diffusion chambers over 54 to 56 days of in situ exposure to a polar marine environment (-1.8 degrees C; salinity, 34.5 ppt) at McMurdo Station, Antarctica. Plate counts were used to assess recoverability and injury, whereas direct viable counts (DVCs) and 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) reduction were utilized to determine substrate responsiveness and respiratory activity, respectively. T90 values (times for 10-fold decreases in numbers of recoverable cells) on nonselective medium were ca. 216 to 259 h for E. coli, S. typhimurium, and Y. enterocolitica and 432 h for E. faecalis. Sublethal injury was greater in populations of indicator bacteria than in pathogens. DVCs, CTC reduction, and plate counts indicated progressive increases in viable but nonculturable cells in E. coli, S. typhimurium, and Y. enterocolitica cultures throughout the 54-day exposure. Forty-eight-day exposure of E. coli, S. typhimurium, and Y. enterocolitica resulted in decreased optimal incubation temperatures for colony formation and inability to form colonies at 37 degrees C. The detection of responsive E. coli, S. typhimurium, and Y. enterocolitica by the DVC and CTC methods remained within 1% of inoculum values during 54 days of exposure, indicating some long-term persistence in the viable-but-nonculturable state. Percentages of respiring E. coli and S. typhimurium increased significantly upon addition of nutrients at all temperatures tested, indicating that nutrient availability rather than temperature limited enteric bacterial activity in this very cold environment. Large nutrient inputs to low-temperature marine environments may thus allow for the long-term persistence of enteric bacteria in a nonrecoverable state.

Cold Temperature↗
PubMed1994

Defective fluid transport by cystic fibrosis airway epithelia.

Cystic fibrosis (CF) airway epithelia exhibit defective transepithelial electrolyte transport: cAMP-stimulated Cl- secretion is abolished because of the loss of apical membrane cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channels, and amiloride-sensitive Na+ absorption is increased two- to threefold because of increased amiloride-sensitive apical Na+ permeability. These abnormalities are thought to alter respiratory tract fluid, thereby contributing to airway disease, the major source of mortality in this genetic disease. However, the underlying hypothesis, that fluid transport is abnormal in CF airway epithelia, has not been tested. Most conjecture about fluid transport is based on measurements of Na+ and Cl- transport performed under short circuit conditions in Ussing chambers. But such studies differ from in vivo conditions in that transepithelial voltage and mucosal fluid composition are held constant. Therefore, we measured fluid transport and mucosal electrolyte composition in primary cultures of CF airway epithelia without holding transepithelial voltage and ion concentration gradients at zero. In normal epithelia, cAMP agonists plus amiloride stimulated NaCl and fluid secretion. In CF epithelia, cAMP agonists failed to stimulate fluid or electrolyte secretion, changes consistent with the loss of CFTR Cl- channels. But in striking contrast to predictions based on Ussing chamber studies, CF epithelia absorbed fluid at a rate no greater than normal epithelia. Moreover, amiloride, which inhibits Na+ channels, failed to inhibit fluid absorption by CF epithelia. These results have important implications for understanding the pathogenesis of CF airway disease and for the design and evaluation of therapy.

Amiloride↗
PubMed1994

The effects of halothane and isoflurane on cerebrocortical microcirculation and autoregulation as assessed by laser-Doppler flowmetry.

The effects of volatile anesthetics on red blood cell flow in the cerebral microcirculation have not been compared. We used laser-Doppler flowmetry, which measures red blood cell flow in the microcirculation to compare the effects of differing concentrations of isoflurane and halothane on cerebrocortical microcirculation. Sprague-Dawley rats were anesthetized with pentobarbital (65 mg/kg intraperitoneally). The animals were tracheotomized, paralyzed, and artificially ventilated. In the first protocol laser-Doppler flow (LDF) was recorded at 0.5, 1, 1.5, and 2 minimum alveolar anesthetic concentration (MAC) halothane or isoflurane, with blood pressure controlled by intravenous phenylephrine infusion (0.5-5 micrograms.kg-1.min-1). In the second protocol the effects of 0.5 and 1.5 MAC halothane and isoflurane on LDF changes in response to changes in mean arterial blood pressure (MABP) were compared. MABP was increased by phenylephrine infusion and decreased by hemorrhage. LDF increased with each 0.5 MAC increase in halothane and isoflurane concentration (P < 0.05). LDF was greater at 1.5 and 2 MAC isoflurane than at equi-MAC halothane (P < 0.01). Autoregulation of LDF was present but attenuated at MABP of 60-140 mm Hg at low halothane and isoflurane concentrations. LDF was increased at 1.5 MAC vs 0.5 MAC for both drugs (P < 0.01). The autoregulation coefficients (percent LDF change/mm Hg MABP change) were 0.41 +/- 0.10, 0.42 +/- 0.07, 0.27 +/- 0.04, and 0.20 +/- 0.05 at 0.5 MAC halothane, 0.5 MAC isoflurane, 1.5 MAC halothane, and 1.5 MAC isoflurane, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Host response profiles: a new theory to help us understand why and how attractants attract.

Much insect behavior is better described in terms of response profiles than by classical stimulus-response patterns; the response to a particular stimulus may vary with changing internal and external conditions, making it important to qualify statements such as "compound X is an attractant." Because of the large number of conditions that may affect responses, it is crucial to develop a theoretical basis to direct the collection of field and experimental data, and their interpretation. A theory-driven model can help us predict response profiles over a wide range of such conditions. We describe an example of such a model, the assumptions upon which it is based, how the model is constructed, and the types of results that a computer implementation of the model can produce.

Animals↗
PubMed1993

Testicular torsion and its effects on contralateral testicle.

Twenty-six male adult Noble (Nb) rats underwent unilateral left testicular torsion of 720 degrees. The testicles of the 6 control animals were immediately detorsed. The experimental animals were divided into 4 groups according to the surgical approach (abdominal vs. scrotal) and location where the torsed testicle was placed (abdomen vs. scrotum). After six hours all torsed testicles in the experimental groups were detorsed. One month later all animals were sacrificed, and the contralateral testicles were examined for spermatogenesis and mean seminiferous tubular diameter. All groups displayed decreased spermatogenesis with smaller mean seminiferous tubular diameter as compared with the control group.

Animals↗
PubMed1993

Localization of ribosomal DNA in Rhagoletis pomonella (Diptera: Tephritidae) by in situ hybridization.

The ribosomal DNA (rDNA) of Rhagoletis pomonella was localized within both salivary gland polytene chromosomes and somatic cell mitotic chromosomes by in situ hybridization using the heterospecific Drosophila melanogaster rDNA clone, Dm238. In situ hybridization analysis of polytene nuclei showed that R. pomonella rDNA is located in the nucleolus and adjacent granular network of chromosome 1. The site of origin of rDNA is within this isomorphic granular network. The preservation of nucleolar ultrastructure in some polytene chromosome preparations allowed light microscope localization of R. pomonella rDNA to the apparent periphery of fibrillar centres within fibrillar complexes. In somatic cell nuclei, DM238 hybridized to the nucleolus organizing region (NOR) located on chromosome 1 at the site of the secondary constriction. The frequency distribution of heteromorphisms for rDNA content, differential appearance of secondary constrictions, non-pairing of the NOR and differences in homologue lengths suggests that the structural differentiation of this region in chromosome 1 is sex linked. This the first published description of the salivary gland polytene chromosomes from R. pomonella, and we include a tentative karyotype description, polytene chromosome maps and comments on their suitability for banding and molecular analysis.

Animals↗
PubMed1993

Fluid and electrolyte transport by cultured human airway epithelia.

An understanding of the fluid and electrolyte transport properties of any epithelium requires knowledge of the direction, rate, and regulation of fluid transport and the composition of the fluid. Although human airway epithelial likely play a key role in controlling the quantity and composition of the respiratory tract fluid, evidence for such a role is not available. To obtain such knowledge, we measured fluid and electrolyte transport by cultured human nasal epithelia. Under basal conditions we found that epithelia absorbed Na+ and fluid; both processes were inhibited by addition of amiloride to the mucosal surface. These data suggest that active Na+ absorption is responsible for fluid absorption. Interestingly, Na+ absorption was not accompanied by the net absorption of Cl-; some other anion accompanied Na+. The combination of cAMP agonists and mucosal amiloride stimulated the secretion of NaCl-rich fluid. But surprisingly, the response to cAMP agonists in the absence of amiloride showed substantial intersubject variability: cAMP stimulated fluid secretion across some epithelia, for others, cAMP stimulated fluid absorption. The explanation for the differences in response is uncertain, but we speculate that the magnitude of apical membrane Na+ conductance may modulate the direction of fluid transport in response to cAMP. We also found that airway epithelial secrete H+ and absorb K+ under basal conditions; both processes were inhibited by cAMP agonists. Because the H+/K(+)-ATPase inhibitor, SCH 28080, inhibited K+ absorption, an apical membrane H+/K(+)-ATPase may be at least partly responsible for K+ and H+ transport. However, H+/K+ exchange could not entirely account for the luminal acidification. The finding that cAMP agonists inhibited luminal acidification may be explained by the recent finding that cAMP increases apical HCO3- conductance. These results provide new insights into how the intact airway epithelium may modify the composition of the respiratory tract fluid.

Amiloride↗