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Biomedical subjects

J F White

Publications and source records attributed to J F White.

At least 73 records · Page 4Linked to original sources
PubMed1986

Adrenergic agents stimulate and cholinergic agents inhibit H+ secretion by amphibian jejunum.

In vitro segments of Amphiuma jejunum secrete H+ spontaneously. This study explored the effect of cholinergic and adrenergic agents on H+ secretion. Segments of mucosa were short-circuited and exposed on their mucosal surface to HCO3- -buffered medium while the pH of the unbuffered serosal medium was held by the pH-stat technique. Methacholine added to the serosal medium nearly abolished the spontaneous short-circuit current (Isc) and serosal alkalinization (JHCO3-) with an EC50 of 3.7 X 10(-7) M. Subsequent addition of norepinephrine (NE) to the serosal medium caused a dose-dependent increase in Isc and JHCO3. For three catecholamines the order of potency was epinephrine greater than NE greater than isoproterenol. The spontaneous Isc was significantly reduced (P less than 0.05) by the gastric H+-K+-ATPase inhibitor omeprazole, while the NE-induced Isc was unaltered by the inhibitor. Replacement of medium Na+ with choline abolished the response to NE. The NE-induced Isc was also reduced by methacholine. Acetazolamide inhibited the spontaneous and NE-induced Isc and JHCO3. In summary, cholinergic and adrenergic agents have opposing effects on intestinal H+-HCO3- transport. Jejunal acid secretion may be controlled in part by these antagonistic influences. Adrenergically activated acid secretion occurs by a different mechanism than spontaneous acid secretion.

Acetazolamide↗
PubMed1986

Effects of age on the adaptive behavior of institutionalized individuals with Down syndrome.

Institutional residents with Down syndrome (N = 413) were matched on sex, length of hospitalization, and IQ with an equal number of residents in other diagnostic categories. The subjects were divided into six age groups, from 0 to 19 to 60 to 69 years, and comparisons were made on 62 items of the Client Development Evaluation Report. Significant effects of age were found on 38 items and of diagnosis, on 19 items, but significant Age X Diagnosis interaction effects on only 4 items. Thus, there was little evidence that age differentially affects the adaptive behavior of mentally retarded persons with and without Down syndrome.

Activities of Daily Living↗
PubMed1985

Omeprazole inhibits H+ secretion by Amphiuma jejunum.

The effect on HCO3- absorption of the substituted benzimidazole omeprazole, an inhibitor of active H+-K+ exchange, was examined in in vitro Amphiuma jejunum. HCO-3 absorption was measured using titration in short-circuited intestinal segments bathed in a Cl--free (SO2-(4)-based) medium (pH 7.40). At 1 mM omeprazole lowered the short-circuit current (Isc) and the absorptive flux of HCO3- from mucosa to serosa by about 40% over 1 h. When the serosal medium was maintained at pH 5.0, additions of omeprazole beginning at 0.1 mM caused proportional reductions of the Isc. Omeprazole also reduced intracellular potassium activity (aiK) from 74 to 59 mM and lowered the luminal membrane potential (psi m) slightly over 30 min when this was measured with double-barreled, K+-sensitive microelectrodes. After 30 min aiK and psi m tended to spontaneously revert toward control values. Galactose added to the mucosal medium (to 20 mM) stimulated the Isc equally in omeprazole-treated tissues and paired untreated control tissues. These results support the view that a fraction of the absorptive HCO3- flux (so-called) is driven by an active luminal exchange of H+ for K+.

Animals↗
PubMed1985

Adaptive behavior of institutionalized individuals with Down syndrome.

Institutional residents with Down syndrome (N = 413) were matched with an equal number of residents in other diagnostic categories with respect to sex, age, length of hospitalization, and IQ. The two groups were compared on 62 items of the Client Development Evaluation Report, and significant differences were found on 19 of these items. The subjects with Down syndrome tended to show greater social competence (except in the clarity of their speech) and less maladaptive behavior. To account for these differences, we offer the speculative hypothesis that the favorable expectations of service providers for their clients with Down syndrome may come to serve as self-fulfilling prophecies.

Activities of Daily Living↗
PubMed1984

Electrogenic Cl- absorption by Amphiuma small intestine: dependence on serosal Na+ from tracer and Cl- microelectrode studies.

The Na+ requirement for active, electrogenic Cl- absorption by Amphiuma small intestine was studied by tracer techniques and double-barreled Cl- -sensitive microelectrodes. Addition of Cl- to a Cl- -free medium bathing in vitro intestinal segments produced a saturable (Km = 5.4 mM) increase in short-circuit current (ISC) which was inhibitable by 1 mM SITS. The selectivity sequence for the anion-evoked current was Cl- = Br- greater than SCN- greater than NO-3 greater than F- = I-. Current evoked by Cl- reached a maximum with increasing medium Na concentration (KM = 12.4 mM). Addition of Na+, as Na gluconate (10 mM), to mucosal and serosal Na+-free media stimulated the Cl- current and simultaneously increased the absorptive Cl- flux (JCl m----s) and net flux ( JClnet ) without changing the secretory Cl- flux ( JCls ----m). Addition of Na+ only to the serosal fluid stimulated JClm ----s much more than Na+ addition only to the mucosal fluid in paired tissues. Serosal DIDS (1 mM) blocked the stimulation. Serosal 10 mM Tris gluconate or choline gluconate failed to stimulate JClm ----s. Intracellular Cl- activity ( aiCl ) in villus epithelial cells was above electrochemical equilibrium indicating active Cl- uptake. Ouabain (1 mM) eliminated Cl- accumulation and reduced the mucosal membrane potential (psi m) over 2 to 3 hr. In contrast, SITS had no effect on Cl- accumulation and hyperpolarized the mucosal membrane. Replacement of serosal Na+ with choline eliminated Cl- accumulation while replacement of mucosal Na+ had no effect. In conclusion by two independent methods active electrogenic Cl- absorption depends on serosal rather than mucosal Na+. It is concluded that Cl- enters the cell via a primary (rheogenic) transport mechanism. At the serosal membrane the Na+ gradient most likely energizes H+ export and regulates mucosal Cl- accumulation perhaps by influencing cell pH or HCO-3 concentration.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1984

Microelectrode measurements of K+ and pH in rabbit gastric glands: effect of histamine.

Conventional and liquid ion-exchange microelectrodes sensitive to K+ or pH were used to examine the response of isolated rabbit gastric glands to histamine. The epithelial cells were impaled across the basolateral membrane. The membrane potential averaged -6.1 +/- 0.6 mV and was unchanged after replacement of medium K+, Cl-, or Na+. The intracellular K+ activity (alpha iK) averaged 41.3 +/- 3.0 mM, indicating K+ accumulation by a factor of 6.8. Active accumulation of K+ was eliminated by ouabain. In contrast, histamine increased K+ activity to 55.3 +/- 3.9 mM. This stimulation was blocked by ouabain. In glands bathed in a Na+-free medium containing ouabain, addition of histamine elevated alpha iK from 12.5 +/- 0.7 to 17.1 +/- 1.1 mM. Isobutylmethylxanthine (10(-4) M) also elevated alpha iK. When impaled with pH-sensitive microelectrodes, glands exposed to histamine exhibited regions of acidity as low as pH 3. Acidification was also produced by histamine after medium Na+ had been replaced with choline. Picoprazole (H 149/94) blocked the effects of histamine on alpha iK and gland pH. The results are consistent with the view that histamine-induced acid secretion by gastric glands is associated with K+ uptake by a mechanism that is independent of Na+ transport but is inhibited by intracellular Na+. This is most likely the H+-K+-ATPase on the secretory surface of the gland cells. Evidence that some tissue K+ is bound or compartmentalized is also discussed.

1-Methyl-3-isobutylxanthine↗
PubMed1984

Association between HCO3(-) absorption and K+ uptake by Amphiuma jejunum: relations among HCO3(-) absorption, luminal K+, and intracellular K+ activity.

Titration techniques and K+- sensitive microelectrodes have been used to investigate the relations among HCO3(-) absorption, luminal K+, and intracellular K+ activity in in vitro Amphiuma jejunum. The HCO3(-) absorptive flux (JHCO3(-] measured by pH-stat under short circuit was reduced by removal of K+ from the medium but not by replacement of Na+ with choline. JHCO3(-) exhibited a seasonal variation when K+ was absent from the media and was increased to a maximum when K+ equaled 5 mM. Addition of K+ to a K+-free luminal medium stimulated JHCO3(-) much more than addition to the serosal medium. Acetazolamide (10(-4) M) blocked K+-stimulated HCO3(-) absorption while benzolamide reduced the short-circuit current associated with HCO3(-) absorption much more rapidly when added to the mucosal bathing medium. Intracellular K+ activity (aik) and mucosal membrane potential (psi m) of jejunal villus cells were measured with double-barreled microelectrodes. When bathed bilaterally with HCO3(-)-containing media, K+ was actively accumulated for many hours (aik = 58.5 mM) but in the presence of ouabain fell to equilibrium (16 mM) after 2 h. In contrast, when HCO3(-) absorption was induced by removal of serosal HCO3(-), aik was elevated to 83.6 mM and, after 4-h exposure to ouabain cell K+, remained far above electrochemical equilibrium at 33 mM. Tissues bathed in Na+-free (Tris) media containing ouabain retained cell K+ after 4 h at even higher levels (46 mM). Cell K+ activity was reduced by removal of K+ from either the mucosal or serosal medium. Acetazolamide reduced aik over 2 h in Na+-free media from 66 to 42 mM. The decline in aik was associated with a concomitant decline in the HCO3(-) absorptive current. It is concluded that K+ is actively accumulated across both luminal and serosal membranes of the jejunal absorptive cell and that the luminal uptake mechanism is linked to HCO3(-) absorption or an equivalent process.

Absorption↗
PubMed1984

Office videofiberoptic laryngoscopy.

Precise photographic documentation is of significant importance for proper diagnosis and management of physiological and pathological conditions of the larynx. Since the fiberscope serves an important role in the daily practice of laryngologists, its value is greatly enhanced when coupled with a video camera. Fiberoptic videolaryngoscopy permits instant and simultaneous voice and visual recordings for later study. The procedure is most useful for analysis of respiration, phonation, singing, and other laryngeal functions such as glottic closure, swallowing, and protective-compensatory movements. The procedure also allows investigation of various pathological conditions. The purpose of this paper is to present the authors' method of fiberscopic videolaryngoscopy and its relevant clinical implications. Advantages and disadvantages of the procedure are discussed.

Ambulatory Care↗
PubMed1984

Anesthetic considerations at moderate altitude.

The influence that changes in altitude may have on various aspects of anesthetic practice are discussed. The consequences of alterations in the partial pressure and density of anesthetic gases are described, as well as the problems that may arise as a result of using measuring devices calibrated in percentages that actually measure partial pressure. The performance of vaporizers under conditions of reduced barometric pressure is considered. The behavior of flowmeters at altitude was studied. The increase in flow produced by flowmeters under hypobaric conditions is not a constant factor dependent on density, but is variable at flow rates below 4 L/min. The following suggestions are put forward. Anesthetists should be encouraged to think in terms of the partial pressures of gases that they are using rather than concentrations. Measuring devices and vaporizers that are dependent on partial pressure and not on concentration should be calibrated in the appropriate units. The term MAC could be replaced by MAPP, which would more accurately represent the important factor in the delivery of anesthetic gases. The value of nitrous oxide in anesthetic practice at altitude needs to be reassessed.

Altitude↗
PubMed1983

Cardiac arrhythmogenic action of benzo(a)pyrene in the rabbit.

Rabbits treated with benzo(a)pyrene developed cardiac arrhythmias when exposed by inhalation to 8100 ppm trichloroethylene or 15000 ppm halothane to a greater extent and at lower doses of epinephrine challenge than did controls. Benzo(a)pyrene and 3-methylcholanthrene both increased the metabolism of trichloroethylene, but 3-methylcholanthrene did not increase its cardiotoxic effect. The basis of the arrythmogenic action of benzo(a)pyrene appears to be unrelated to its ability to induce xenobiotic metabolism.

Animals↗
PubMed1983

A role for basolateral anion exchange in active jejunal absorption of HCO-3.

Isolated short-circuited segments of jejunum from Amphiuma absorbed HCO-3 at a rate determined by the anion composition of the bathing media. The rate of HCO-3 absorption (JHCO-3) measured by pH-stat was high when the major anion was Cl-, Br-, I-, or SO2-(4) but was lower when gluconate or benzene sulfonate (SO-3) was the anion. The disulfonic stilbenes SITS, DIDS, and DNDS at 1 mM reduced JHCO-3 and short-circuit current when added to the serosal bathing medium. Inhibition by SITS was comparable whether Cl-, Br-, or SO2-(4) was the major anion, and SITS produced a small inhibition of JHCO-3 in gluconate-based media and no effect in benzene SO3-based media. Under conditions in which tissue conductance was low SITS lowered tissue conductance further. In Cl- media SITS reduced short-circuit current consistent with inhibition of Cl- absorption as well as HCO-3 absorption. Inhibition of the Cl- current by DIDS was not reversed by washout, although the inhibition of JHCO-3 was reversed. The rate of HCO-3 absorption in gluconate media could be increased by serosal addition of Cl-, Br-, or I-. It is concluded that the process that results in net jejunal HCO-3 absorption entails anion-HCO-3 exchange at the basolateral membrane and is distinct from the basolateral Cl(-)-HCO-3 exchange process involved in Cl- absorption.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1982

Intestinal electrogenic HCO3- absorption localized to villus epithelium.

Isolated segments of jejunum from Amphiuma absorb HCO3+ electrogenically by a process sensitive to acetazolamide. Using a tissue chamber of special design which permits isolation of villus or intervillus epithelium the transepithelial electrical potential (psi ms) of each region was measured. The serosa-negative psi ms generated by the villus epithelium was more negative than that of the intervillus and exhibited greater sensitivity to acetazolamide. Both regions were responsive to other agents which alter epithelial ion transport. The results indicate that intestinal HCO3- absorption is localized predominantly within cells lining the villus epithelium.

Acetazolamide↗
PubMed1982

Intestinal HCO3- secretion in Amphiuma: stimulation by mucosal Cl- and serosal Na+.

The requirement for Na+ and Cl- in the bathing media to obtain a maximal HCO3- secretory flux (JHCO3-) across isolated short-circuited Amphiuma duodenum was investigated using titration techniques and ion substitution. Upon substitution of media Na+ with choline, HCO3- secretion was markedly reduced. Replacement of media Cl- produced a smaller reduction of JHCO3-. The presence of Cl- enhanced HCO3- secretion only if Na+ was also in the media. Elevation of media Na+ or Cl- in the presence of the other ion produced a saturable increase of JHCO3-. In the presence of Na+, Cl- stimulated JHCO3- when added to the mucosal but not the serosal medium. In the presence of Cl-, Na+ elevated JHCO3- when added to the serosal but not the mucosal medium. The ability of mucosal Cl- to stimulate JHCO3- was not apparently dependent on mucosal Na+. Simultaneous addition of 10 mM Cl- to the Na+ -free mucosal medium and 10 mM Na+ to the Cl- -free serosal medium stimulated JHCO3- above levels produced by serosal Na+ alone. In conclusion, intestinal HCO3- secretion required mucosal Cl- and serosal Na+ and did not involve mucosal NaCl cotransport. The results are consistent with a mucosal Cl- absorptive mechanism in series with parallel basolateral Na+ -H+ and Cl- -HCO3- exchange mechanisms.

Animals↗