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Biomedical subjects

J A Mitchell

Publications and source records attributed to J A Mitchell.

At least 235 records · Page 13Linked to original sources
PubMed1983

Serotonin-induced disruption of implantation in the rat: I. Serum progesterone, implantation site blood flow, and intrauterine pO2.

Serotonin, administered on the day after the initiation of implantation, promptly terminates pregnancy in the rat. Consequently, the effects of serotonin on serum progesterone levels, implantation site blood flow, and intrauterine oxygen tension were determined to see whether the disruption of implantation is related to altered corpus luteum and/or uterine vascular function. Animals received a subcutaneous injection of physiological saline (C: control) or serotonin (S: 20 mg/kg) on Day 5 of pregnancy. Serotonin did not alter the number of blastocysts implanting (C: 6.02 +/- 0.52 vs. S: 6.29 +/- 0.46, sites/cornu) but did cause subsequent implantation site resorption (C: 0.08 +/- 0.07 vs. S: 5.46 +/- 0.44/cornu; P less than 0.001). Progesterone levels in serotonin-treated rats did not differ from those of controls at 6 h postinjection or on Days 6 through 10 of pregnancy. Implantation site blood flow was reduced at 30 min (C: 0.76 +/- 0.12 vs. S: 0.25 +/- 0.02 ml/min per g; P less than 0.01) and remained suppressed at 2 h after serotonin injection. A prompt and sustained reduction in intrauterine oxygen tension (C: 48.9 +/- 3.7 vs. S: 25.9 +/- 4.5 mmHg; P less than 0.005; 120 min) accompanied the reduced uterine perfusion. Thus, disruption of implantation is not a result of impaired corpus luteum function but is associated with marked and protracted reductions in uterine blood flow and intraluminal oxygen availability.

Animals↗
PubMed1983

Serotonin-induced disruption of implantation in the rat: II. Suppression of decidualization.

Subcutaneous injection of serotonin (20 mg/kg) on Day 5 of pregnancy disrupts implantation in the rat as indicated by the reduction in number of live fetuses/cornu present on Day 19 (0.9 vs. 6.1, treated vs. control). Such disruption of implantation possibly results from impaired decidualization. To test for suppression of decidualization, serotonin was administered to pseudopregnant rats on the day before, on (Day 4) or after artificial induction of the decidual cell reaction. Relative to saline-treated controls (C), serotonin (S) reduced decidualization when injected either before [C: 1987 +/- 130 vs. S: 1085 +/- 155 mg (Day 3); P less than 0.005] or after [C: 1987 +/- 130 vs. S: 173 +/- 8 mg (Day 5); P less than 0.001] administration of the deciduogenic stimulus. In addition, serotonin markedly decreased uterine blood flow (C: 0.47 +/- 0.05 vs. S: 0.25 +/- 0.06 ml/min per g; P less than 0.01) during pseudopregnancy. However, serotonin altered neither the duration of luteal function in pseudopregnant rats (C: 15.3 vs. S: 14.3 days) nor serum progesterone levels (C: 74-91 vs. S: 53-82 ng/ml) in pregnant animals. It is concluded that serotonin may disrupt implantation, in part, by suppression of decidualization. The loss of endometrial competence to undergo decidualization appears to be a consequence of serotonin-induced uterine ischemia rather than impaired corpus luteum activity.

Animals↗
PubMed1981

Deletions of different segments of the long arm of chromosome 4.

We report the clinical and chromosomal findings in 8 patients with deletions of the long arm of chromosome 4. Four of these patients appear to have terminal deletions beginning in band 4q31, and therefore, lack the digital 1/3 of the long arm of chromosome 4. We confirm that deletion of 4q31 leads to qter causes a recognizable syndrome, and we further define the phenotype of that syndrome. A 5th patient has a horter terminal deletion, ie, 4q33 leads to qter. This deletion causes a milder phenotypic expression than that seen in the severe 4q terminal-deletion syndrome. The remaining 3 patients have interstitial deletions of the long arm of the 4th chromosome, including segments 4q21.1 leads to q25, 4q21.3 leads to q26, and 4q27 leads to q31.3. The phenotypic expression noted in these patients is variable in differs from the 4q terminal-deletion syndrome.

Abnormalities, Multiple↗
PubMed1981

Effects of nicotine on uterine blood flow and intrauterine oxygen tension in the rat.

Subcutaneous injection of nicotine (0.5 or 5 mg/kg body wt) resulted in a marked and prolonged reduction in uterine blood flow and intrauterine oxygen tension in pseudopregnant rats. By 10 min after nicotine administration (5 mg/kg) uterine perfusion was reduced by 40%, remained suppressed for 90 min and returned to the pre-treatment level by 120 min. Rats receiving the 0.5 mg nicotine/kg also showed a marked reduction in uterine blood flow, although the response was slower in onset and longer in duration. Nicotine (5 mg/kg) also resulted in a sustained decrease in intrauterine oxygen tension from a control value of 48.9 +/- 3.6 to 22.2 +/- 2.6 mmHg at 45--60 min and 21.7 +/- 1.5 mmHg at 60--90 min. The frequency and amplitude of fluctuations in intrauterine oxygen tension were still reduced by 90 min after treatment.

Animals↗
PubMed1980

GENFILES: a computerized medical genetics information network. I. An overview.

GENFILES is a comprehensive computer information network to serve research, service, and administrative needs in medical genetics. Four major databases contain detailed information generated by the cytogenetics laboratory, the prenatal diagnosis program, the diagnostic and genetic counseling clinics, and the human cell culture facility. Unique aspects are the use of RAMIS, a commercial database management system, and of microprocessor computers as "intelligent" terminals with significant data-handling capabilities. All databases are no-line in a directly accessed large timesharing computer. The system, which has been designed, controlled and maintained by regular genetics staff, is an easy to use, moderate-cost tool well suited for use as a regional clinical genetics information system.

Computers↗
PubMed1980

GENFILES: a computerized medical genetics information network. II. MEDGEN: the clinical genetics system.

MEDGEN, a clinical genetics information storage and retrieval system, facilitates the handling of medical records for the central genetics clinic and satellite clinics conducted by the University of California, San Francisco. The system is part of the GENFILES genetics network, which handles all of the genetics data generated by a comprehensive medical genetics center. The clinical data stored on each patient include 1) diagnoses, which utilize McKusick catalog numbers as well as our own diagnostic codes; 2) relevant medical, gestational, and pregnancy history; 3) clinical manifestations (functional and structural); 4) karyotype information through a crosslink to the cytogenetics file; 5) ethnic origin of the patients; 6) physical status and sex of the patient; 7) laboratory studies, including results of metabolic tests; and 8) any additional remarks deemed necessary for complete understanding. The data, staff member attending, and physical location of each visit also are recorded.

Computers↗
PubMed1980

Scanning electron microscopy of brain ventricular surfaces: a bibliography.

This bibliography is designed to facilitate the rapid identification and location of references concerning the application of scanning electron microscopy to investigations of the cerebroventricular system and related cerebrospinal fluid contacting surfaces. Because SEM provides information regarding cell surfaces, it is admirably suited to the examination of the brain ventricular system since the morphology of the CSF interface is of the utmost importance in accomplishing the diverse functions of the ependyma and associated circumventricular organs. The bibliography attests to the fact that scanning electron microscopy has provided a major impetus to the study of the structure and function of the circumventricular organs, choroid plexuses and tanycytic ependyma as well as the distribution and morphology of such supraependymal cellular elements as macrophages, neurons, and neuronal proceses. Furthermore, not only are SEM methodologies being applied to an ever lengthening list of phyla and species, but the diversity of problems amenable to the profitable application of scanning electron microscopy also is rapidly increasing. Investigations to date, for example, include studies of ventricular morphology during development and maturity, health and disease, and prior to as well as following experimental manipulation. While remarkable strides have been made toward a greater understanding of many aspects of cerebroventricula structrure and function, many significant problems clearly await the judicious application of scanning electron microscopy.

Bibliographies as Topic↗
PubMed1979

Morphology and distribution of type II supraependymal cells in the third ventricle of the guinea pig.

The distribution and morphology of phagocytic (Type II) supraependymal cells residing within the third ventricle of the guinea pig were investigated by scanning electron microscopy. Type II supraependymal cells were restricted to nonciliated regions of the ventricle. They were most numerous on the choroid plexus, abundant within the infundibular recess and were present on the ventricular floor in the region of the median eminence. Morphologically, they were characterized by a soma from which pseudopodia-like processes extended to the subjacent ependyma. Type II cells varied in configuration according to their location. Those residing on the choroid plexus typically had irregular somas and possessed processes that generally terminated in finger-like extensions. In contrast, cells on the ventricular floor and within the infundibular recess were stellate and possessed processes that terminated in fan-like cytoplasmic expansion. There were no differences noted in the frequency, distribution or morphology of Type II supraependymal cells in male and female animals. Furthermore, cell frequency did not appear to vary in relation to the estrous cycle. The data suggest that the pleomorphism exhibited by Type II supraependymal cells may reflect adaptations to diverse environmental conditions present within different regions of the third ventricle.

Animals↗
PubMed1978

Electron microscopic demonstration of a supraependymal cluster of neuronal cells and processes in the hamster third ventricle.

A supraependymal cluster of neuronal cells and processes consistently present on the floor of the hamster third ventricle was identified and characterized by means of correlative scanning (SEM) and transmission (TEM) electron microscopy. SEM revealed each cluster to be ovoid with the majority of its surface covered by dome-shaped protrusions and fine beaded fibers. A number of processes traveling individually or in groups also entered or exited from the cluster at its base. As these processes passed over the ventricular surface, they contributed to an extensive network on the floor and ventral aspect of the ventricular wall. Some processes terminated on the ependymal surface in bulbous endings while others penetrated the ependyma. The neuronal nature of these clusters and their associated processes was confirmed at the TEM level. The dome-shaped protrusions visible on the surface of the cluster in SEM corresponded to apical surfaces of neurons confined to the peripheral aspect of a core of loosely arranged processes. These cells exhibited a prominent nucleolus, stacks of rough endoplasmic reticulum (RER), polyribosomes, Golgi cisternae, mitochondria and microtubules (MT) and gave rise to dendritic processes which extended into the core. These dendrites gave off branches at acute angles and contained polyribosomes, single cisternae of RER and evenly spaced MT. Other profiles of processes within the core shared these characteristics, suggesting that they also were branches of the peripheral cells. Axons present within the core and on the cluster's surface exhibited vesicle-filled varicosities which frequently established synaptic contact with the peripheral cells and their processes. The presence of an intraventricular cluster of neurons which potentially communicates with centers extrinsic to the ventricle may have important implications in the hypothesized role of cerebrospinal fluid and tanycytic ependyma in the neuroendocrine regulation of anterior pituitary function.

Animals↗
PubMed1978

Supraependymal neurons overlying the periventricular region of the third ventricle of the guinea pig: a correlative scanning--transmission electron microscopic study.

The frequency of occurrence, distribution and morphology of supraependymal neurons associated with the third ventricular wall of the guinea pig were investigated by correlative scanning and transmission electron microscopy. Each of the specimens was located on the ciliated ventricular wall between the inferior border of the thalamus and the non-ciliated ependyma associated with the median eminence. Prominent clusters of neuronal perikaria in association with massive process bundles were observed in 7 of the 31 specimens examined. In those specimens lacking prominent neuronal networks a more diffuse array of independent nerve fibers was sometimes seen on the ependymal surface. Neuronal perikaria exhibited numerous surface protrusions and were covered by a rich meshwork of crisscrossing, varicosed fibers. Many of these cells were associated with multiple processes of varying diameters and lengths which either coursed independently over the ventricular surface or formed fasciculated bundles. As process bundles traversed the ependymal surface, individual processes branched off and either terminated within the ventricular lumen or penetrated the subjacent ependymal lining. Fibers also made contact with adjacent supraependymal neuronal elements. Correlative transmission electron microscopic observations indicate that both the perikaria and processes of such supraependymal networks possess ultrastructural features characteristic of neurons. The morphological characteristics of the intraventricular neuronal networks suggest that they may be engaged in functional interactions with the cerebrospinal fluid, with adjacent supraependymal neuronal elements and with the subjacent neuropil.

Animals↗