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Biomedical subjects

L M Lewin

Publications and source records attributed to L M Lewin.

At least 55 records · Page 3Linked to original sources
PubMed1983

Carnitine and short-chain acylcarnitines in the lumen of the human male reproductive tract.

Bioautography of human semen demonstrated the presence of L-carnitine, acetylcarnitine, propionylcarnitine and C4-acylcarnitines (butyrylcarnitines). In studies designed to ascertain the organs secreting these compounds into semen it was found that: Quantitative analyses of semen obtained pre- and post-vasectomy showed markedly decreased L-carnitine concentrations, slightly decreased acetylcarnitine levels, and unchanged propionyl- and butyrylcarnitine concentrations as a result of vasectomy. The earlier portion of human split ejaculate samples characteristically contained higher concentrations of carnitine and its propionyl- and butyryl esters and a lower concentration of acetylcarnitine than did the later portion. Vas deferens luminal fluid contained carnitine and each of the short-chain acyl derivatives, as shown by bioautography. Prostatic fluid contained only small amounts of carnitine and its derivatives. Spermatozoa contained much more acetylcarnitine than free carnitine, and only trace amounts of the other acylcarnitines. It is concluded that carnitine in semen is secreted primarily by the epididymis, that a proportion of the acetylcarnitine derives from the seminal vesicles and epididymis, and that propionylcarnitine and butytylcarnitine enter semen, at least in part, together with the vas deferens contents.

Adult↗
PubMed1982

myo-inositol in the reproductive tract of the female rat.

1. myo-Inositol concentrations in oviduct, ovary and uterus were many-fold those of blood serum during all four stages of the estrous cycle of the female rat. 2. Inositol concentration was higher in oviduct than in ovary or uterus and was lower in uterine fluid than in uterus. 3. Estrus uteri had higher inositol concentrations than uteri in other phases of the cycle. 4. In order to measure dynamic aspects of the distribution of inositol, the distribution of radioactivity among organs of the reproductive tract of mature female rats was measured 45 min after i.p. injection of [2-3H]myo-inositol. 5. These organs concentrated inositol from the blood, and the tissue radioactivity (expressed as dpm/mg wet wt of tissue) increased in the sequence: vagina less than cervix less than uterus less than ovary less than oviduct. 6. The uterus and ovary concentrated myo-inositol more strongly during proestrus than during metestrus, diestrus of estrus. 7. The contents of proestrus follicles were more highly radioactive than was the ovary itself, whereas proestrus uterine fluid was less radioactive than the uterine tissue.

Animals↗
PubMed1982

A comparative study of carnitine and acylcarnitine concentration in semen and male reproductive tract fluids.

1. L-carnitine and its short-chain acyl derivatives were measured in semen of boar, man, rooster, bull, squirrel monkey and ram. 2. Carnitine was present in concentrations of 220, 476, 540, 1880, 3330 and 3820 muM respectively, and acetylcarnitine concentrations were 2, 191, 354, 709, 259 and 2750 muM. Propionyl and C4-acyl carnitines were found in small quantities. 3. Analysis of sequential "Split-ejaculate" samples of boar semen showed that carnitine concentration correlated with sperm count, suggesting an epididymal origin for this substance in this species. 4. Bioautographic analysis of samples obtained from ram and rat indicated that carnitine and acetylcarnitine were present in epididymal fluid and in fluids from accessory glands of the male reproductive tract.

Animals↗
PubMed1982

The role of sperm-bound hyaluronidase in the dispersal of the cumulus oophorus surrounding rat ova.

Only a very small portion (4-7%) of the hyaluronidase of rat sperm obtained from the caput or cauda epididymis was related during incubation in capacitation medium for up to 24 h at 37 degree C. A portion of the cell-associated hyaluronidase was accessible to external substrates, allowing sperm suspensions to lyse glycosaminoglycans of cumulus clots rapidly, even without capacitation. This process appears to represent the employment of an enzyme bound to the sperm cell, analogous to the use of solid-phase enzymes in current enzyme technology.

Animals↗
PubMed1981

Carnitine and acylcarnitines in semen from azoospermic patients.

Carnitine and its short-chain acyl esters were assayed in semen from normospermic and azoospermic men. Extremely low concentrations of free carnitine and acylcarnitine were found in semen from patients with obstructive azoospermia where the ejaculate was primarily of prostatis origin, and low values were also obtained in obstruction of the vas deferens, where the epididymal contents were not ejaculated. Semen from patients whose azoospermia was caused by testicular dysfunction had low acylcarnitine concentrations and normal levels of free carnitine in most cases, but a group of patients with severe testicular failure (including cases of Klinefelter syndrome and cryptorchidism) had low semen free carnitine concentrations. Whereas treatment with human chorionic gonadotropin increased serum testosterone levels in azoospermic patients, it did not increase the free carnitine concentration in semen, although it increased the proportion of carnitine found in acylcarnitines.

Acetylcarnitine↗
PubMed1979

Percentage agreement and phi: A conversion table.

STUDIES IN APPLIED BEHAVIOR ANALYSIS HAVE USED TWO EXPRESSIONS OF RELIABILITY FOR HUMAN OBSERVATIONS: percentage agreement (including percentage occurrence and percentage nonoccurrence agreement) and correlational techniques (including the phi coefficient). The formal relationship between these two expressions is demonstrated, and a table for converting percentage agreement to phi, or vice-versa, is presented. It is suggested that both expressions be reported in order to communicate reliability unambiguously and to facilitate comparison of the reliabilities from different studies.

Journal Article↗
PubMed1979

Differences in concanavalin A-FITC binding to rat spermatozoa during epididymal maturation and capacitation.

Rat spermatozoa from the caput epididymis and cauda epididymis, but not from the testis, demonstrated a crescent of greenish fluorescence on the convex surface of the sperm head, as observed by fluorescence microscopy after staining with concanavalin A-fluorescein isothiocyanate. The percentage of spermatozoa displaying this fluorescent zone decreased during incubation under capacitating conditions, both in vivo and in vitro, suggesting that a glycoprotein zone that is capable of binding concanavalin A was removed or altered during the capacitation period.

Animals↗
PubMed1978

Variable shock-free times with informative and uniformative stimuli.

Three rats were trained on a fixed-ratio escape procedure in which responding produced one of two equiprobable outcomes-a 10-second or 60-second shock-free period. Before the fixed-ratio requirement was satisfied, brief shocks were presented at irregular intervals averaging either 15 or 30 seconds. Two conditions, differing in the relationship between exteroceptive stimuli and the outcomes, were studied. In the uninformative (uncorrelated) condition, the same stimulus was presented during both outcomes. In the informative (correlated) condition, one stimulus was present during the 10-second outcome only; another stimulus was present during the 60-second outcome only. Subjects pressed faster in the uninformative condition than they did in the informative condition. The inadequacy of the information hypothesis in accounting for the findings is discussed, and an alternative hypothesis is offered.

Journal Article↗
PubMed1978

Hyaluronidase release from guinea pig spermatozoa as affected by reproductive tract secretions and metabolic inhibitors.

Cauda epididymal sperm of mature guinea pigs were incubated (37 degrees, 5% CO2 in air). 10% of the total enzyme activity was released into the medium in 4 hr, 30% in 24 hr. Addition of lysolecithin resulted in rapid release of hyaluronidase. Vitamin C (0.54 mM), sodium fluoride (0.02 M), and cholesterol increased the rate of release whereas citrate (20 mM) diminished it. No effect upon hyaluronidase release was noted upon addition of KCN (10(-2)M), progesterone (250 microgram/ml), testosterone (500 microgram/ml), spermine (1.15 mg/ml), inositol (5.6 mM), or chloroquine phosphate (0.54 mM).

Animals↗
PubMed1977

Paper chromatographic estimation of fructose and myo-inositol in human seminal fluid: a method for evaluating seminal vesicle and prostatic function.

A semiquantitative paper chromatographic method for the separation of myo-inositol and fructose in human seminal fluid was described. The intensity of the chromatographic zones characteristic of myo-inositol, which is a marker for human prostatic secretion and for fructose, which is useful in evaluating seminal vesicle function, were estimated after staining with an alkaline silver nitrate reagent. Characteristic patterns were found for patients with prostatic or vesicular dysfunction, and for patients with agenesis or blockage of the vas deferens. Paper chromatographic analysis of split ejaculate samples allowed evaluation of the sequence of ejaculation of the prostate and seminal vesicles.

Chromatography, Paper↗
PubMed1976

Elevated myo-inositol concentrations in cerebrospinal fluid of neonates and of patients with an impaired state of consciousness.

A simple, semiquantitative paper chromatographic method was used to identify samples of cerebrospinal fluid containing elevated concentrations of myo-inositol. All patients whose CSF inositol concentrations were greater than 70 mug/ml (as determined by S. carlsbergensis microbiological assay) showed disturbances of the state of consciousness, reported as stupor, coma or confusion in adults, or apathy and stupor in infants. An elevated level of inositol in cerebrospinal fluid appeared to be a characteristic finding in infants under one year of age. Among other age groups no common etiology was correlated with high inositol concentration.

Adolescent↗
PubMed1976

Studies on the metabolic role of myo-inositol. Distribution of radioactive myo-inositol in the male rat.

Radioactive myo-inositol was injected intraperitoneally into nephrectomized rats. The radioactive material present in liver, spleen, brain, heart, diaphragm, seminal vesicle, coagulating gland, prostate, epididymis, vas deferens and testis was shown to consist exclusively of myo-inositol and its derivatives, as shown by paper chromatography of hydrolysates and trichloroacetic acid extracts of these tissues. Radioactive myo-inositol was accumulated rapidly within 1 h by the thyroid, coagulating gland and seminal vesicle. Other tissues, such as the pituitary, prostate gland, liver and spleen, concentrated myo-inositol less actively. The muscle tissues studied (diaphragm and heart) concentrated little inositol, whereas brain, testis, and epididymal fat-pad did not concentrate it at all. The lipid fraction of liver contained most of the radio-labelled myo-inositol. In the other organs most of the radioactivity was found in the aqueous trichloroacetic acid extract, largely as free myo-inositol.

Animals↗
PubMed1976

Epididymis and seminal vesicle as sources of carnitine in human seminal fluid: the clinical significance of the carnitine concentration in human seminal fluid.

Carnitine determinations in human seminal fluid were shown to be useful in assessing epididymal and seminal vesicle function and in locating blockages in the male reproductive tract. The carnitine concentrations in 50 samples of seminal fluid ranged from 15 to 530 mug/ml (as carnitine-HCl). The patients could be divided into four classes. Patients with normal seminal vesicle and epididymal function had values of 250 mug/ml or above. Those with a defective epididymis and a functional seminal vesicle had intermediate carnitine levels (100 to 200 mug/ml) and normal fructose values in the seminal fluid. Patients with a defective seminal vesicle but a functional epididymis had intermediate carnitine concentrations and low fructose levels. Extremely low carnitine values (less than 100 mug/ml) were found in seminal fluid from patients whose epididymis and seminal vesicle both were defective. The possible role of carnitine in sperm maturation was discussed.

Acid Phosphatase↗