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R J Levin

Publications and source records attributed to R J Levin.

At least 73 records · Page 4Linked to original sources
PubMed1990

Endometrial electrogenic ion secretion in the rat is modulated by prostaglandins.

In the isolated rat uterus, maximal increases in endometrial electrogenic ion secretion produced by luminal prostaglandins (PGs) E1, E2 and F1, and measured as the short-circuit current (Isc), displayed bell-shaped dose-response curves. PGE1 was the most potent and PGF1 the least. The dose-response relationships for the decrease in resistance were curvilinear for PGE1 and PGF1 but bell shaped for PGE2. PGF1 was the most potent at inhibiting the increase in Isc induced by serosal adrenaline but not in inhibiting the fall in tissue resistance. The electrogenic ion secretion of rat endometrium is modulated by prostaglandins via a mechanism also influenced by adrenaline.

Animals↗
PubMed1990

Rectal electrogenic secretion--is it a putative indicator of intestinal secretory status induced by nutritional deprivation in the rat?

Intestinal secretion is enhanced by starvation in rats. The rectum from fed and 3-day-starved rats generates a basal electrogenic ion transfer (short-circuit current) in vitro which is mainly electrogenic Na+ absorption (amiloride-sensitive, 66-71%) with a small component of electrogenic chloride secretion (furosemide-sensitive, 14-22%). Bethanechol, a muscarinic agonist, caused an increase in the short-circuit current (mainly furosemide-sensitive chloride secretion) and potential difference in rectums from both fed and starved rats but the respective values for the starved animals were 100% and 64% greater. In starvation, the rat rectum is an indicator of intestinal secretory status. The result warrants investigation of human rectal electrogenic secretion in nutritional deprivation.

Absorption↗
PubMed1990

Diarrhoea of famine and malnutrition: investigations using a rat model. 1. Jejunal hypersecretion induced by starvation.

The effects of progressive starvation for up to three days on the secretory functions of the intestine were investigated using in vitro and in vivo preparations of rat jejunum and secretagogues whose action was either through cyclic AMP or Ca++. Initial starvation for 24 h (day 1) did not significantly alter the basal net electrogenic ion secretion measured in vitro as the short circuit current (Isc, muamps/cm2) or the change in electrogenic ion secretion (delta Isc) induced by the secretagogues. By day 2 of starvation, however, the maximum delta Isc transient induced by the cholinergic and other secretagogues (delta Isc = Isc max-basal Isc) was greatly increased (up to a maximum of 117%) compared with the fed controls on an area basis. The delta Isc were even greater on day 3 of starvation. If a tissue weight basis was used to normalise the data the increase became even more marked. The enhancement in secretion was not caused by a decrease in absorptive capacity as glucose, added mucosally, gave larger increases in absorptive currents in the starved than in the fed jejuna. Bethanecol dose-delta Isc response curves in fed and starved jejuna showed an increase in the maximum electrogenic secretion in the starved but no apparent change in the affinity of their cholinergic receptors mediating the enhanced secretion. The starvation-induced increase in secretion elicited by bethanecol was blocked by atropine, indicating that the receptors were muscarinic, but was unaffected by tetrodotoxin indicating that the enteric neural innervation was not essential for its expression. Noradrenaline released by tyramine was greater in the starved than the fed jejunum, suggesting that a decreased sympathetic tone was unlikely to be the major cause of the starvation induced secretory enhancement. Measurement of jejunal fluid movements in vivo showed that in fed controls and throughout the three days of starvation there was an unchanged net fluid absorption in the basal, unstimulated state. By day 2 and day 3 of starvation, however, bethanecol stimulated fluid secretion was very much greater than that of the fed controls. This increase in fluid secretion was concomitant with significant increases in the concentration of chloride in the lumenal fluid. Starvation thus appears to make the rat jejunum hypersensitive to cholinergic and other secretagogues, increasing the electrogenic secretion of chloride in vitro and that of chloride and fluid in vivo. These results obtained with the rat model give a new insight into possible mechanisms by which the diarrhoea of human famine and malnutrition may be expressed.

Animals↗
PubMed1990

Diarrhoea of famine and malnutrition--investigations using a rat model. 2--Ileal hypersecretion induced by starvation.

The effects of progressive starvation for up to three days on the basal and secretagogue stimulated secretory functions of the rat ileum were investigated in vitro and in vivo. The secretagogues used included agents acting via cyclic AMP (dibutyryl cyclic AMP, theophylline, forskolin, and PGE2) and those acting via Ca++ (acetylcholine, bethanecol, carbachol, 5-hydroxytryptamine, and A23187). Starving rats for 24 h (day 1) had no effect on the basal electrogenic secretion (measured as the short circuit current, Isc muamps/cm2) or on the stimulated maximum electrogenic secretion (measured as the delta Isc where delta Isc = maxIsc-basal Isc). By day 2 of starvation, however, both the basal Isc and the delta Isc induced by all the secretagogues were significantly greater than in the fed and increased even more on day 3. Replacement of all the chloride ions and inhibition by furosemide indicated that the enhanced secretion was due mainly to chloride ions. Cholinergic stimulation was blocked by atropine, indicating the stimulation was via muscarinic receptors while cholinergic dose - delta Isc response curves for fed and starved ilea showed significantly increased maximum electrogenic secretory response in the latter but no evidence of any change in the affinity (ED50) of the receptors mediating the response. The basal secretion and the secretory response to acetylcholine in both fed and starved ilea was unaffected by tetrodotoxin, revealing that the enhanced secretory response could be expressed via the muscarinic receptors on the enterocytes without the enteric neural network. Measurement of ileal fluid movement in vivo showed that in fed and day 1 starved rats the basal, unstimulated 'tone' of the ileum was absorptive. On day 2, however, the basal 'tone' had reversed to one of secretion which increased further on day 3. Stimulation of fluid secretion in vivo by bethanecol, carbachol, or PGE2 induced larger increases in the starved ilea by day 2 which increased even further on day 3. Lumenal chloride and bicarbonate concentrations were greater in the starved ileal fluid than in the fed. The studies in rat ileum confirm and extend those on rat jejunum and indicate that starvation creates a hypersensitive small bowel that responds to secretagogues and cholinergic neurotransmitters with a greatly enhanced secretory response.

Acetylcholine↗
PubMed1990

Empowering families of the chronically ill: a partnership experience in a hospital setting.

An intervention model has been developed which teaches family members, in partnership with social workers, to obtain and monitor services for their chronically ill elderly relatives. The research site is a Boston teaching hospital with a patient population that is ethnically and racially diverse. Initial results of the study reveal that case management is easily accepted by most families, and the partnership between the family member and social worker enhances the delivery of needed services.

Aged↗
PubMed1989

Structure and expression of a muscle specific gene which is adjacent to the Drosophila myosin heavy-chain gene and can encode a cytochrome b related protein.

We report the characterization of a transcription unit at the second chromosome locus 36B, designated TU-36B which is adjacent to the 3' end of the Drosophila myosin heavy-chain (Mhc) gene. We have isolated and sequenced a complementary DNA clone and the region of genomic DNA which represents this gene. The sequencing studies reveal that this gene contains one intron, the mRNA is 1480 nucleotides in length, the TU-36B mRNA is transcribed in an orientation opposite to the Mhc mRNAs, and the poly(A) addition site of this gene is 99 nucleotides downstream of poly(A) addition site A-2 of the Drosophila Mhc gene. The mRNA contains a continuous open reading frame which can encode a protein product of 47,000 daltons in molecular weight. The proposed protein shares homology with cytochrome b proteins. Comparison of in situ hybridization of Mhc specific and TU-36B specific probes to tissue sections demonstrates that both mRNAs are predominantly transcribed in the same muscle tissues of the developing fly.

Amino Acid Sequence↗
PubMed1989

Electrical activity of corpus cavernosum during flaccidity and erection of the human penis: a new diagnostic method?

We investigated 7 normal men and 1 diabetic patient with erectile dysfunction. Electromyography electrodes were placed in the corpus cavernosum of the penis and electrical activity was recorded during flaccidity. With sexual arousal the activity decreased and tumescence was initiated. During tumescence and full erection the electrical activity of the corpus cavernosum almost ceased but in the diabetic patient (neurogenic impotence) an increase was observed. This discoordination might be the cause of the erectile dysfunction. Recording the electrical activity of the corpus cavernosum in patients with suspected neurogenic erectile dysfunction could become clinically valuable, since this is the first test possible to study the function of the autonomic motor system that normally regulates penile function.

Adult↗
PubMed1989

The rat distal ileum has a reduced absorptive and secretory capacity compared with proximal ileum--is it to facilitate its chemosensing function?

Compared with the proximal ileum, the distal ileum in rat has a greatly reduced capacity for electrogenic ion secretion induced by secretagogues and for electrogenic, sodium-linked glucose transfer assessed in vitro. Similarly, in vivo, there is a great reduction in distal ileal basal fluid absorption and secretagogue-activated fluid secretion compared with proximal ileal values. This reduced absorptive and secretory capacity of the distal ileum would allow minimal changes in the concentrations of the luminal contents, facilitating its putative role as final chemosensor of the luminal contents of the small intestine.

Acetylcholine↗
PubMed1988

Diaphragm insertion increases human vaginal oxygen tension.

The normal insertion of a contraceptive diaphragm into the vagina of five young women induced a dramatic increase in the vaginal oxygen tension (131 +/- 13 mm Hg, mean +/- SD, n = 5), which slowly fell at an initial rate of 0.9 +/- 0.2 mm Hg/min. Withdrawal of the diaphragm immediately restored vaginal oxygen tension to the normal hypoxic state (11 +/- 12 mm Hg). The change in gaseous equilibrium created by the trapped air of the diaphragm could have significant actions on the microbial activity and balance of the vagina.

Adult↗
PubMed1988

Structure/activity relationships of a homologous series of surfactants (nonyl-phenoxypolyethoxyethanols) on rat vaginal bioelectric activity over the oestrous cycle.

The spermicide nonoxynol-9 is a member of a homologous series of alkylphenol-ethoxylates (polyethoxyethanols) of general formula C9H19-C6H6-O-(CH2CH2O)n-1 CH2CH2OH. Nonoxynol-9 when instilled into the vagina of anaesthetized rats causes a rapid fall in the transvaginal potential difference (p.d.). Using the time taken for the p.d. to fall to half its value (t 1/2), the structure/activity relationship of a number of isosmolar solutions of the compounds on the vaginal p.d. was assessed during the oestrous cycle. Members of the series tested had n = 1.5, 4, 6, 8/9, 9, 10/11, 15, 20, 30 and 40 and were commercially available (Antarox CO series, GAF). At pro-oestrus all compounds were ineffective. At metoestrus and oestrus the relationship between the activity of the series and the n value was clearly U-shaped, a similar pattern was apparent at dioestrus. When n = 40, 30 or 20 little or no effect was observed on the p.d. but the depressive activity was significant at n = 15 and became maximal at n = 8/9 and 9. When n = 6 the activity began to attenuate while at n = 4 and 1.5 it became very reduced. The relation between the ability to depress the p.d. and the moles of ethylene oxide (n) appeared to be related to the hydrophilic/hydrophobic balance of the compound. When n was greater than 15 the compounds were too hydrophilic to enter the membrane phase and cause disruption while when n less than 6 they were too hydrophobic and had too small a molar volume to affect membrane function.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Bioelectric activity as a quantifiable index of acute spermicide (nonoxynol-9) actions on rat vaginal epithelial function during the oestrous cycle.

The acute effect of instillation of the spermicide 2% nonylphenoxypolyethoxyethanol (nonoxynol-9) on the bioelectric activity of the vaginal epithelium was assessed using as an index the time taken in seconds to reduce the transvaginal potential difference (p.d.), measured in anaesthetised rats, to half its initial value (t1/2). The surfactant caused rapid falls in the p.d. at dioestrus (t1/2 = 35 +/- 25 sec., n = 16, mean +/- S.D.) and metoestrus (t1/2 = 32 +/- 27 sec., n = 11) with a slower fall at oestrus (t1/2 = 130 +/- 104 sec., n = 14). At pro-oestrus however, nonoxynol-9 had no effect (n = 18). The dye Nigrosin (0.5%), when instilled alone, did not stain untreated vaginas of anaesthetized rats at any stage of the oestrous cycle, but in the presence of 2% nonoxynol-9 heavily stained those in metoestrus and dioestrus. Vaginas in pro-oestrus were unstained while those in oestrus were stained lightly. While nonoxynol-9 has a dramatic effect on the bioelectric activity of the vaginal epithelium, both the electrical and dye data show that the pro-oestrus vaginal epithelium presents a significant diffusion barrier to the passage of nonoxynol-9 and nigrosin. Thus, in assessing the actions of vaginally instilled nonoxynol-9 in rats the variation in the permeability of the vaginal epithelium during the oestrous cycle must be taken into account.

Aniline Compounds↗
PubMed1986

Absorption of menstrual discharge by tampons inserted during menstruation: quantitative assessment of blood and total fluid content.

The simultaneous absorption of genital secretions and blood was assessed in 61 intravaginal tampons from eight young, healthy, nulliparous volunteers during menstruation. The tampons were self-inserted over the first 3 days of menstruation according to the habit of each subject. Wide variations in the amount of blood and fluid absorbed were noted within and between subjects. The mean amount of genital secretion absorbed was 0.31 g/h and that of menstrual blood was 0.76 g/h. The average tampon absorbed 65% blood and 35% genital secretion.

Absorption↗
PubMed1985

Orgasm in women in the laboratory--quantitative studies on duration, intensity, latency, and vaginal blood flow.

Sexual arousal by clitoral self-stimulation was used by healthy, young adult women volunteers (n = 28) to induce orgasm in the laboratory. The duration of the orgasm was obtained using the subject's verbal indication of its start and finish. The estimated duration and the subjective experience of the orgasm self-graded on a 5-point scale were also obtained in a number of subjects. Vaginal blood flow was assessed by the power consumption needed to keep a heated oxygen electrode, held on the vaginal wall by suction, at a constant temperature. The mean measured orgasm duration was 19.9 seconds (SD, +/- 12, n = 26). For 14 subjects, their estimate of the duration of their orgasms (12.2 +/- 9.8 seconds, mean +/- SD) was greatly underestimated compared with the measured duration (26 +/- 14.6 seconds). This result indicates that data obtained on the duration of orgasm from questionnaires or interviews have suspect validity. The measured duration of the orgasms was not significantly correlated with the subjective grading. The increase in vaginal blood flow at orgasm was not significantly correlated with the subjective gradings of orgasm (n = 18), the orgasm latency (time taken to induce orgasm, n = 18), or the measured duration of orgasm (n = 14).

Adult↗
PubMed1984

Problems involved in correlating changes of functional diffusive and anatomical surface areas of the upper and lower chicken small intestine during fasting.

The anatomic villous surface area and the functional diffusive area (measured by the absorption of 64 mM thiourea) of the jejunum and ileum was estimated in fed and 3-d-fasted chickens. In the jejunum, fasting caused a 50% reduction of the anatomic villous surface area but only a 32% reduction in the functional diffusive area. The jejunal permeability to thiourea was unaltered. The ileal anatomic villous surface area was unaffected by fasting but the ileal functional diffusive area was decreased significantly by 26%, concomitant with a significant reduction of 34% in the permeability to thiourea. The passive absorption of thiourea cannot be used as a simple index of the functional diffusive surface area for dietary-induced changes in the small intestine of the domestic fowl.

Animals↗
PubMed1983

Comparison of jejunal and ileal absorptive functions for glucose and valine in vivo--a technique for estimating real Km and Jmax in the domestic fowl.

1. A technique is described that enables the kinetic characterisation of the saturable absorption mechanisms in the chicken jejunum and ileum for glucose and valine in vivo (after correction for non-saturating components and unstirred layers) by estimation of real Km and Jmax. 2. In the ileum both nutrients have lower real Km and higher Jmax values than in the jejunum indicating, at least for hexose and amino acids, that the ileal enterocytes are functionally equipped and anatomically well-sited to fulfil the role of scavengers of the small intestine.

Animals↗
PubMed1983

Rat endometrial bioelectric activity in vivo and in vitro: effects of adrenaline.

The transuterine potential difference (p.d.) generated by the endometrium was measured in vivo in anaesthetized, ovariectomized rats treated with 10 micrograms oestradiol-17 beta each day for 3 days. Intravenous injection of adrenaline induced transient hyperpolarization of the p.d.; sigmoid dose-dependency was observed over the range 2-40 micrograms/kg. Pre-treatment of the rats with syrosingopine shifted the dose-response curve to the left (enhancement) while combined propranolol (800 micrograms/kg) and phentolamine (800 micrograms/kg) shifted the dose-response curve to the right (depression). Isoprenaline gave similar quantitative changes in the p.d. in vivo which displayed a similar time course and sigmoid dose-dependency. Propranolol alone (800 micrograms/kg) shifted this dose-response curve significantly to the right. Addition of adrenaline or isoprenaline to the serosal solution bathing uteri incubated in vitro after removal from oestradiol-treated rats induced changes in endometrial bioelectric activity that exhibited sigmoid dose-response curves for the transuterine p.d. and short-circuit current (Isc). Propranolol significantly shifted the dose-response curves for adrenaline to the right. Only adrenaline caused small but significant decreases in the uterine resistance but these were not dose-dependent. Acetylcholine, 5-hydroxytryptamine, noradrenaline and phenylephrine had no effect on the transuterine p.d. in vivo or in vitro or on the Isc in vitro. No significant electrical changes could be induced by adrenaline or any of the other drugs across the uteri from untreated ovariectomized rats either in vivo or in vitro. The transluminal membrane p.d. of surface endometrial cells measured with micro-electrodes was depolarized by an addition of serosal adrenaline but only 41% of the cells successfully impaled responded in this way. The results indicate that endometrial cells under oestrogen stimulation possess electrogenic processes that can be modulated specifically by adrenaline through the mediation of a serosally sited beta-adrenoceptor. The physiological role of the mechanism has yet to be established.

Animals↗