Biomedical subjects

M L Adams

Publications and source records attributed to M L Adams.

At least 55 records · Page 3Linked to original sources

PubMed1991

Stereoselective effect of morphine on antinociception and endogenous opioid peptide levels in plasma but not cerebrospinal fluid of dogs.

Morphine releases endogenous opioids into the circulation of dogs. To test the stereospecificity of this effect, as well as to determine whether morphine also releases endogenous opioids centrally, which might be involved in its antinociceptive action, the effects of (-)-morphine sulfate (10 mg/kg, sc) or (+)-morphine hydrobromide on antinociception in a dog tail-flick test, on semi-quantified morphine-induced signs of salivation, emesis, defecation and ataxia, and on the plasma and cerebrospinal fluid (CSF) levels of endogenous opioid peptides were studied. Plasma and CSF levels of immunoreactive beta-endorphin (i-BE), met-enkephalin (i-ME), leu-enkephalin (i-LE), and dynorphin (i-DY) were quantified by radioimmunoassay in octadecylsilyl-silica cartridge extracts. Immunoreactive morphine (i-M) levels were measured in unextracted samples. (-)-Morphine treatment significantly increased antinociception, morphine-induced signs, i-M levels in plasma and CSF, and i-BE, i-ME, and i-LE levels in plasma, but not CSF. Levels of i-DY remained constant in plasma and CSF. (+)-Morphine treatment did not alter any of these parameters, indicating that the effects of morphine on nociception, behavioral signs, and plasma endogenous opioids in dogs were stereoselective. It is concluded that morphine does not cause an increase in immunoreactive endogenous opioid peptides in the CSF at the time of its peak antinociceptive effect.

Animals↗

PubMed1991

Effects of alcohol on beta-endorphin and reproductive hormones in the male rat.

In an attempt to examine the relationship between alcohol-induced alterations in immunoreactive beta-endorphin (i-beta E) levels in the hypothalamic-pituitary-gonadal axis and the synthesis and release of reproductive hormones, male rats were treated with either an acute intraperitoneal injection of alcohol or were chronically exposed to an alcohol-containing liquid diet. Hypothalamic, pituitary, serum, and testicular levels of immunoreactive beta-endorphin (i-beta E) and serum levels of luteinizing hormone (LH) and testosterone were measured at various times after initiation of these treatments. Testicular interstitial fluid (TIF) volumes and levels of TIF i-beta E and testosterone were also measured 4 hr after acute treatment as an index of testicular release of these substances. Acute alcohol decreased pituitary levels of i-beta E and increased serum levels of the peptide for up to 1 hr after its injection, but did not alter hypothalamic or testicular levels. Acute alcohol markedly increased TIF i-beta E and decreased TIF testosterone and TIF volume. Sharp decreases in serum LH and testosterone were observed in association with these acute changes in i-beta E levels in the pituitary, blood, and testes. During chronic alcohol exposure serum testosterone levels were substantially depressed, but tolerance appeared to develop quickly to the chronic effects of alcohol on serum LH. Similarly, tolerance to alcohol's effects on i-beta E levels in the pituitary and serum also appeared to develop during chronic alcohol administration. However, hypothalamic and testicular i-beta E levels were markedly suppressed by chronic alcohol administration in contrast to the lack of effect observed after acute alcohol administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Alcohol affects rat testicular interstitial fluid volume and testicular secretion of testosterone and beta-endorphin.

The effects of alcohol on testicular interstitial fluid (TIF) volume and the secretion of testosterone and beta-endorphin (beta E) into this important testicular compartment were assessed in the rat. Alcohol time- and dose-response curves were constructed for changes in TIF volume and the bioactive concentrations of testosterone and immunoreactive beta E (i-beta E). Alcohol (3 g/kg) decreased TIF volumes and increased TIF i-beta E secretion 0.5 to 6 hr after injection and decreased TIF testosterone 1 to 6 hr after injection. These effects were dose-related at 2 hr postinjection. The possible role of alcohol-induced reductions in serum luteinizing hormone and testosterone levels in mediating the effects of alcohol on TIF volume was also examined. We found that pretreating rats with human chorionic gonadotropin, which reversed alcohol-induced suppression in levels of serum gonadotropins and testosterone, failed to reverse the effects of alcohol on TIF volume and the secretion of testosterone and i-beta E. These results indicate that alcohol decreases TIF volume, inhibits TIF testosterone secretion and stimulates TIF i-beta E secretion and, furthermore, suggest that these effects are not indirectly mediated by decreased levels of gonadotropins or testosterone, but by direct effects of alcohol on gonadal function. The strong inverse correlation between TIF i-beta E and testosterone secretion after alcohol administration and previous evidence that testicular opioids inhibit the biosynthesis of testosterone suggest that alcohol may act through testicular beta E to suppress the synthesis and release of testosterone in the testes.

Animals↗

PubMed1991

Influence of morphine exposure during adolescence on the sexual maturation of male rats and the development of their offspring.

The effects of adolescent morphine exposure on the sexual maturation of male rats, their reproductive capacity and the development of their progeny were examined. Groups of prepubescent male rates (25-27 days of age) were implanted with morphine- or placebo-pellets (one on Day 1, then two pellets on Days 4, 7 and 10); the pellets were not removed to assure the sustained release of morphine for 3 to 4 weeks and to avoid the confounding effects of a precipitated withdrawal syndrome. Groups of animals were sacrificed at weekly intervals through adulthood for an assessment of reproductive endocrine function. A large group, however, was also bred with drug-naive primiparous females at 85 days of age (8 weeks after morphine or placebo pellet implantation), when the acute and chronic effects of morphine on reproductive endocrine parameters had dissipated; their fertility and the development of the male and female progeny was characterized. Our results indicated that morphine exposure during adolescence led to a pronounced inhibition of a number of indices of sexual maturation (e.g., serum testosterone and luteinizing hormone levels and reduced weights of the testes and seminal vesicles). Breeding morphine- and placebo-implanted male rats with drug-naive females resulted in smaller liters derived from morphine-treated fathers when compared to controls, but in all other respects the development of the offspring in the two groups were equivalent. However, upon reaching adulthood, a number of selective endocrine differences were detected in morphine-derived offspring when compared to controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Suicidal behaviors among Connecticut youth.

In the United States, youth (15-24 years) suicide rates increased 191% between 1950 and 1986. This paper presents data regarding suicidal ideation and attempts, suicide-related hospitalizations, and completed suicides among Connecticut youth, comparing them with data from other states and the United States. Girls have higher rates of attempts and hospitalization, boys of completed suicide. Firearms are the suicidal method of choice for both sexes. Nonmetropolitan areas had higher rates than metropolitan. Reported suicidal ideation among students ranged from 10% to as high as 66%, while attempts range from 3% to 15%. The authors stress that caution is necessary when comparing rates, pointing to the need for standardized data collection and analysis. Reported rates of suicidal behavior are lower among Connecticut youth compared to their counterparts in other states, but suicide is increasing among young males in Connecticut and remains a major issue for health care providers.

Adolescent↗

PubMed1990

Effectiveness of steam autoclaving on the contents of sharps containers.

The effectiveness of steam autoclaving on bacterial endospores placed within five types of sharps containers was tested. A variety of container physical orientations within the autoclave were evaluated. Spores were present on commercial spore strips or placed onto capped and uncapped dental needles. All strips and needles present in empty or filled containers could be sterilized within 15 minutes when the containers were placed on their sides and their vents left open. The contents of containers processed in an upward position required between 30-60 minutes of autoclaving before being sterilized. The size and shape of the containers influenced ease of sterilization.

Dental Instruments↗

PubMed1990

The medical management of acute appendicitis in a nonsurgical environment: a retrospective case review.

The treatment of acute appendicitis in remote environments without the capability of surgical intervention appears to be effective when using antibiotic protocols active against both aerobic and anaerobic bacteria. A review of nine such cases treated with various antibiotic protocols was conducted and demonstrated good response in all patients. This aggressive medical management frequently resulted in complete resolution of symptoms in patients who later required elective appendectomy or who had recurrences, with similar symptoms requiring acute appendectomies. A strong index of suspicion for appendicitis must be maintained in these cases and one must rely on the medical documentation of the initial episode and proceed with a thorough surgical evaluation.

Acute Disease↗

PubMed1990

Influence of chronic alcohol administration on representative indices of puberty and sexual maturation in male rats and the development of their progeny.

The effects of chronic alcohol administration on reproductive endocrinology in the developing male rat were examined. Prepubescent male rats (25 days of age) were maintained on an alcohol liquid diet or were pair-fed a control diet until early adulthood and selected indices of sexual maturation were examined at weekly intervals. To determine whether sexually immature animals were more sensitive to the effects of alcohol than adults, fully mature male animals were exposed to an identical period of alcohol exposure and comparisons were made between the two groups. The results demonstrated that alcohol significantly affected many of the primary indices of puberty and sexual maturation. The normal pubertal increases in serum testosterone levels, the weights of the testes and secondary sex organs and beta-endorphin levels in the hypothalamus were substantially reduced in alcohol-exposed animals compared with controls. In contrast to these results, the effects of alcohol on reproductive endocrinology in the fully mature animal were transitory and of considerably less magnitude. After a 2-week alcohol-free period, male rats exposed to alcohol during development were bred with drug-naive primiparous females. Although the same number of pregnancies resulted from matings between alcohol-exposed males and drug-naive females compared with controls, litter sizes were significantly smaller in alcohol-derived offspring than in controls. In all other respects, such as body weights, sex ratios, mortality rates and gross developmental features (eye opening, incisor eruption and testes descent), alcohol-derived offspring were identical with controls. Upon closer examination, however, significant disturbances were detected in alcohol-derived male offspring.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

The effects of inhibition of heme synthesis on the intracellular localization of iron in rat reticulocytes.

These studies assessed the fate and localization of incoming iron in 6-8-day rat reticulocytes during inhibition of heme synthesis by succinylacetone. Succinylacetone inhibition of heme synthesis increased iron uptake by increasing the rate of receptor recycling without affecting receptor KD for transferrin, transferrin uptake, or total receptor number. Its net effect was to amplify the number of surface transferrin receptors by recruitment of receptors from an intracellular pool. Despite increased iron influx in inhibited cells, only 2-4% of total incoming iron was diverted into ferritin. The majority of incoming iron (65-80%) in succinylacetone-inhibited cells was recovered in the stroma, where ultrastructural and enzymic analyses revealed it to be accumulated mainly in mitochondria. Intramitochondrial iron (70-75%) was localized mainly in the inner membrane fraction. Removal of succinylacetone restored heme synthesis, utilizing iron accumulated within mitochondria for its support. Thus, inhibition of heme synthesis in rat reticulocytes results in accumulation of incoming iron in a functional mobile intramitochondrial precursor iron pool used directly for heme synthesis. Under normal conditions, there is no significant intracellular or intramitochondrial iron pool in reticulocytes, which are therefore dependent upon continuous delivery of transferrin-bound iron to maintain heme synthesis. Ferritin plays an insignificant role in iron metabolism of reticulocytes.

Animals↗

PubMed1989

The ontogeny of immunoreactive beta-endorphin and beta-lipotropin in the rat ovary.

We have investigated the ontogeny of, and the effect of hypophysectomy on, immunoreactive beta-endorphin in rat ovaries. Total levels rose with ovarian weight from nondetectable levels at 5 days of age to approximately 0.15 pmol/ovary at 80 days; thereafter, the levels remained constant through 201 days of age. Hypophysectomy decreased both ovarian weight and the total content of immunoreactive beta-endorphin, but the concentration per weight was not significantly altered. Most of the immunoreactive beta-endorphin before puberty chromatographed like authentic beta-endorphin, but after puberty most chromatographed like beta-lipotropin. Hypophysectomy did not alter this chromatographic pattern.

Aging↗

PubMed1989

The ontogeny of immunoreactive beta-endorphin and beta-lipotropin in the rat testis.

We have investigated the ontogeny of immunoreactive beta-endorphin (i-beta E) in the testes of rats from 5 to 150 days of age. i-beta E was measured by RIA in acid extracts of decapsulated testes and characterized by gel filtration chromatography. Significant age-related differences in both the levels and type of i-beta E were observed. Total levels of i-beta E in the testes were very low and barely detectable from 5-20 days of age, but rose sharply in parallel with testes weights from 20-60 days of age; thereafter, no significant changes in i-beta E were found through 150 days of age. Concentrations of i-beta E, expressed in pmol/g testis, fell precipitously between days 5 and 10 and remained relatively constant from 10-150 days. Most of the i-beta E at 5 and 15 days chromatographed like authentic beta-endorphin. However, with the onset of puberty (30-35 days) and during sexual maturation, much of the total i-beta E chromatographed like its' precursor beta-lipotropin (beta LPH). Hypophysectomy decreased the weight and total i-beta E levels of the testes to the same extent without altering the concentrations of i-beta E or the chromatographic pattern of i-beta E. These results indicate that beta E-like and beta LPH-like peptides are present in the rat testis and that age-related changes in both the levels and type of i-beta E correlate with various structural and functional aspects of testicular development.

Aging↗

PubMed1989

Verbal fluency characteristics of normal and aphasic speakers.

Fourteen mildly aphasic and 14 normal speakers responded to an oral verbal fluency task for five different semantic categories. Retrieved words were scored within each 15-s time interval of a 60-s task as highly representative (i.e., having a high frequency of occurrence in a previous normative study), moderately representative (i.e., having a moderate frequency of occurrence), or highly unrepresentative (i.e., having a low frequency of occurrence). Both speaker groups were affected similarly by category type, and both retrieved words according to prior data-based notions of semantic categorical organization. The two groups differed with respect to the interaction between time intervals and representativeness levels. The different verbal fluency performance of the aphasic subjects was related to both the temporal occurrence of a word within a 60-s response interval and to its representativeness level (prototypicality) within a particular semantic category.

Aged↗

PubMed1989

In vivo evidence for a direct effect of naloxone on testicular steroidogenesis in the male rat.

It has been suggested that endogenous opioid peptides (EOP) exert paracrine or autocrine effects in the testes. To assess this hypothesis, we examined whether naloxone, by blocking the effects of EOP, influenced serum testosterone levels, apart from its effects on LHRH/LH, in the intact male rat. We found that naloxone increased serum LH and testosterone levels over essentially the same time course and produced dose-dependent increases in serum testosterone levels even though LH levels were maximally elevated at all doses. These data are not consistent with the view that naloxone exerts its effects on testosterone exclusively by altering LHRH/LH release. Additional, perhaps more definitive, evidence of a direct effect of naloxone on testosterone's biosynthesis was provided by our observations that 1) naloxone generated increases in serum testosterone levels in male rats in which the naloxone-induced surge in LH was blocked by nembutal; and 2) intratesticular injections of naloxone increased serum testosterone levels without increasing LH. Although these data suggest that naloxone influences steroidogenesis independently of its effects on LH, we found that the antagonist failed to increase serum testosterone levels in hypophysectomized animals or when serum LH levels were allowed to reach undetectable levels in nembutal-blocked animals. Consequently, our data are consistent with the hypothesis that naloxone facilitates the effects of LH on testosterone's biosynthesis rather than exerting an independent effect of its own. Whether the effects observed in these studies represent a negative autocrine effect of EOP on Leydig cells or a paracrine effect on Sertoli cells remains to be determined. Nevertheless, our results provide, to our knowledge, the first in vivo evidence that EOP modulate testicular steroidogenesis in the intact animal.

Animals↗

PubMed1989

Age-related differences in the sensitivity to opiate-induced perturbations in reproductive endocrinology in the developing and adult male rat.

The effects of a single morphine pellet (75 mg) implanted in developing male rats at 27 days of age on reproductive endocrine parameters were compared to those found in adult (65-day-old) animals after the same treatment. The pellets were left in place to provide the release of morphine during critical phases of puberty and sexual maturation and to prevent an abrupt withdrawal syndrome upon pellet removal which would confound our results. Developing rats were sacrificed at representative intervals after pellet insertion to assess the development of key indices of reproductive endocrinology; adult rats were sacrificed at the same time intervals to permit an evaluation of age-related differences in the sensitivity to opiate-induced endocrine disturbances. Our results showed that morphine markedly influenced a number of endocrine parameters associated with the maturation of the hypothalamic-pituitary-gonadal axis in developing rats for prolonged periods of time, whereas the effects of the opiate in the adult rat were relatively modest and transient. In the developing rat, serum luteinizing hormone (LH), testosterone, the wet tissue weights of the seminal vesicles and testes and hypothalamic LH-releasing hormone (LHRH) levels were substantially depressed immediately after pellet implantation and these effects persisted for up to 4 weeks when compared to placebo-implanted, age-matched controls. In contrast to these results, adult rats showed only transient effects (less than 1 week) of morphine on certain reproductive endocrine parameters (e.g., serum LH, testosterone and the weights of the seminal vesicles) and no effects on others (e.g., testes weights and hypothalamic LHRH).(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed1988

Time-resolved solution X-ray scattering of tobacco mosaic virus coat protein: kinetics and structure of intermediates.

The kinetics of assembly and disassembly of tobacco mosaic virus coat protein (TMVP) following temperature jumps have been studied by small-angle X-ray scattering and turbidimetry. The structures of the principal aggregates of TMVP oligomers (A protein), intermediate size (helix I) and large size helical rods (helix II), have been characterized by their average radii of gyration of thickness, cross section, and shape obtained from the corresponding regimes of the small-angle scattering pattern. This structural information was obtained within seconds after the temperature-induced initiation of either polymerization or depolymerization and allowed us to detect transient intermediates. This methodology made it possible to observe and characterize the structure of a principal intermediate. Taken together with other kinetic information, these data suggest that polymerization of TMVP under virus self-assembly conditions may proceed via a single-layered helical nucleus that contains about 20 subunits. Previous studies have shown that overshoot polymerization of TMVP can occur and results in metastable long helical viruslike rods which subsequently depolymerize and then form short helical rods, depending on the conditions of the final equilibrium state. The longer rods (helix II) are overshoot polymers which form within seconds and contain 17 1/3 subunits per turn (helix IIB), in contrast to the subunit packing arrangement of 16 1/3 subunits per turn found in the shorter helical rods (helix IA). The latter packing arrangement is the one found in TMV. An overall polymerization scheme is proposed for the formation of these two helical forms of TMVP.

Capsid Proteins↗

PubMed1987

Increased cerebrospinal fluid beta-endorphin immunoreactivity in infants with apnea and in siblings of victims of sudden infant death syndrome.

To gain further insight into the possible role of endogenous opioid peptides in the respiratory difficulties associated with the apnea of infancy and other disorders possibly related to apnea, the levels of beta-endorphin immunoreactivity were measured in the cerebrospinal fluid (CSF) of five groups of infants: (1) infants with proved apnea, (2) infants with histories of an apparent life-threatening event (ALTE), (3) siblings of victims of the sudden infant death syndrome (SIDS), (4) infants with suspected but unproved apnea, and (5) infants undergoing investigation for other acute illnesses. Twenty-two infants considered at risk for an ALTE (groups 1 to 3) had significantly higher CSF beta-endorphin equivalents (88 +/- 7 pg/mL) than did the 22 control patients in groups 4 and 5 (31 +/- 3 pg/mL). Plasma beta-endorphin immunoreactivity, which was also measured in some of the infants, did not correlate with levels in CSF and, in fact, was significantly lower in the groups at risk for an ALTE (50 +/- 9 pg/mL; n = 14) than in the control subjects (80 +/- 6 pg/mL; n = 11). These studies indicate that elevated beta-endorphin immunoreactivity in CSF may be a marker in infants who have apnea and who may be considered at risk for an ALTE.

Adult↗

PubMed1987

Increased plasma beta-endorphin immunoreactivity in scuba divers after submersion.

Increased plasma beta-endorphin immunoreactivity in scuba divers after submersion. Med. Sci. Sports Exerc., Vol. 19, No. 2, pp. 87-90, 1987. After submersion under water in a motionless state of neutral buoyancy, scuba divers frequently report feelings of well-being or euphoria similar to those reported after strenuous exercise. Since strenuous exercise is associated with a stress-related increase in plasma beta-endorphin immunoreactivity (beta-EIR), this study was undertaken to measure plasma beta-EIR after submersion in a state of neutral buoyancy under conditions that do not involve strenuous exercise or other extreme stresses. Plasma beta-EIR was measured by radioimmunoassay in male scuba divers before and immediately after remaining motionless 10 ft under water in a state of neutral buoyancy. A significant (P less than 0.01) increase in plasma beta-EIR was found under these conditions. Venipuncture and scuba breathing out of the water did not alter beta-EIR levels. These results indicate that the milder stress associated with submersion in a state of neutral buoyancy involves an increase in plasma beta-EIR similar to that caused by severe stress.

Diving↗

PubMed1986

The role of endogenous peptides in the action of opioid analgesics.

The observation that the narcotic antagonist naloxone could inhibit analgesia produced by electrical stimulation of the brain indicated the involvement of an endogenous chemical in the relief of pain. Multiple endogenous opioid peptides have been identified that have similar pharmacological properties to known narcotic analgesics. The biosynthesis, release, and degradation of opioid peptides have been studied in order to better understand how the manipulation of endogenous opioid systems can be used to produce or augment analgesia. The results of our studies reveal that various conditions and manipulations, such as electrical brain stimulation, acupuncture, stress, and the administration of opioid analgesics, can cause the release of endogenous opioid peptides and possibly endogenous nonpeptide substances. It has also been discovered that nonopioid peptides, such as cholecystokinin, calcitonin, and angiotensin II, can alter the action of opioid analgesics by antagonizing or potentiating their effects. An understanding of the role of endogenous peptides in endogenous opioid mechanisms is necessary for the development of new ways to treat pain and such other disorders as sleep apnea in children (sudden infant death syndrome), head injury, and opioid addiction that involve the activation or alteration of endogenous opioid systems.

Analgesia↗