Search PubMed⌕ Search

Biomedical subjects

A Bortoff

Publications and source records attributed to A Bortoff.

9 recordsLinked to original sources
PubMed1989

Postprandial changes in intestinal slow-wave propagation reflect a decrease in cell coupling.

The purpose of these studies was to determine the effects of feeding on jejunal slow-wave propagation velocity (SWPV). Nine cats were instrumented with six pairs of electrodes implanted 4 cm apart on the jejunum. Electrical activity was recorded at the end of an 18-h fast after which each animal was fed 60 g of canned cat food. Recordings were continued during feeding and for several hours thereafter. This procedure was repeated at least twice for each cat. Average SWPV (cm/s) decreased from a fasting level of 2.28 +/- 0.20 (mean of means +/- SE) to 1.93 +/- 0.16 at 10-20 min, 1.51 +/- 0.11 at 1 h, and 1.37 +/- 0.10 at 3 h postprandially. Corresponding SW frequencies (SWFs) were 19.6 +/- 0.3, 18.7 +/- 0.2, 19.2 +/- 0.2, and 19.0 +/- 0.2 cycles/min, respectively. The differences between the fasting SWPV and that at 1 and 3 h were significant (P less than 0.05). When SWPV was plotted as a function of SWF, the slopes of the corresponding curves were also found to decrease postprandially (P less than 0.05, fasting vs. 1 and 3 h). There was no apparent change in SW amplitude, maximum rate of SW depolarization, or threshold. In the absence of changes in these parameters, the divergence of the slopes at lower SWFs indicates that the decrease in SWPV is because of increased internal resistance, probably the result of uncoupling of intestinal muscle cells. The change is rapid in onset and long in duration, suggesting that an uncoupling factor is released during ingestion of a meal, and that its effect persists for several hours.

Animals↗
PubMed1986

Changes in intercellular electrical coupling of smooth muscle accompanying atrophy and hypertrophy.

Longitudinal tissue impedance was determined for cat circular intestinal muscle that was either hypertrophied due to volume overloading or atrophied due to defunctionalization. These conditions were produced by bypassing 50 cm of jejuno-ileum in six cats and, 2-6 mo later, removing segments from the proximal jejunum of the hypertrophied functional gut and from the atrophied proximal end of the bypassed loop. Impedances were compared with those of jejunal circular muscle from 15 normal cats. Specific tissue impedance was determined by a modification of the method of Tomita (J. Physiol. Lond. 201: 145-159, 1969), which employs Krebs and Krebs-sucrose solutions; a tissue shrinkage of 5%, empirically found to occur in Krebs-sucrose solution, was corrected for. Impedance values were determined at 20 frequencies between 30 Hz and 30 kHz. The value at 30 kHz was taken to represent the specific myoplasmic resistance (Rmyo) of each tissue, while the difference between the value of 30 Hz and 30 kHz was taken to represent the specific junctional resistance (Rj). Values (in omega X cm) for Rmyo were control 134 +/- 2, functional 128 +/- 5, bypassed 151 +/- 6 (mean of means +/- SE). Corresponding values for Rj were control 173 +/- 15, functional 96 +/- 27, bypassed 340 +/- 75. Calculated values (in microF/cm) for junctional capacitance were control 2.66, functional 6.10, bypassed 1.97. Acid uncoupling by saturating the bathing solutions with 100% CO2 revealed a pH-sensitive resistive component of Rj, assumed to be attributable to gap junctions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1975

Stimulation of intestinal smooth muscle by atropine, procaine, and tetrodotoxin.

In order to determine whether or not atropine, procaine, and tetrodotoxin (TTX) can stimulate intestinal smooth muscle directly, we examined the effects of these drugs on the mechanical and electrical activities of several types of cat intestinal smooth muscle preparations. The preparations consisted of isolated rings of 1) intact intestinal wall, 2) intact longitudinal and circular muscle, 3) ganglion-free circular muscle, and 4) ganglion-free circular muscle devoid of its dense layer and plexus muscularis profundus. Atropine and procaine (greater than 10(-4) M) stimulated all four types of preparation. On the other hand, TTX (up to 5 X 10(-6) M) stimulated only preparations 1 and 2. It is concluded that whereas atropine and procaine can directly stimulate intestinal smooth muscle, the excitatory effect of TTX is neurally mediated.

Acetylcholine↗