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Biomedical subjects

M L Berk

Publications and source records attributed to M L Berk.

49 records · Page 3Linked to original sources
PubMed1983

Long descending projections of the hypothalamus in the pigeon, Columba livia.

An autoradiographic analysis was performed on the descending projections of nucleus periventricularis magnocellularis (PVM) of the hypothalamus in the pigeon. A PVM-medullospinal pathway was observed coursing posteriorly through the lateral hypothalamus, ventrolateral midbrain tegmentum, and into the spinal lemniscus (ls) in the ventrolateral pons and medulla. In the pons, some fibers course dorsomedially from ls and terminate at the lateral border of the locus coeruleus. At medullary levels, fibers from ls sweep dorsomedially in the plexus of Horsley and project to certain regions of the nucleus of the solitary tract (NTS) and the dorsal motor nucleus of the vagus (NX). Specifically, PVM fibers project heavily into NTS subnuclei medialis superficialis, medialis ventralis, and lateralis (sulcalis) dorsalis as well as into the ventral parvocellular subnucleus of NX. Fibers in ls were traced caudally into the lateral funiculus as far as upper cervical levels of the spinal cord. Although autoradiographs of lower cervical or thoracic spinal cord sections were not available, PVM fibers do descend to thoracic spinal cord levels, as evidenced by the retrograde transport of horseradish peroxidase. In addition to the medullospinal pathway, the autoradiographs demonstrated PVM projections to septum, diencephalon, and midbrain. Labeled PVM fibers are found in the lateral septal nucleus, nucleus of the anterior pallial commisure, dorsomedial thalamic nucleus, dorsolateral anterior thalamic nucleus (pars ventralis), median eminence, medial and lateral hypothalamus, medial mammillary area, and nucleus intercollicularis and central gray of the midbrain. The projection of fibers to medullospinal regions and median eminence suggests that PVM is homologous to the mammalian paraventricular nucleus. These projections to specific subnuclei of NTS and NX denote hypothalamic control over certain autonomic functions.

Animals↗
PubMed1983

The use and availability of medical care in health manpower shortage areas.

Data from the National Medical Care Expenditure Survey were used to examine access to care and utilization of health services in federally designated health manpower shortage areas (HMSAs). It was confirmed that residents of shortage areas experience some deprivation in access to care and use of services. Further analysis, however, indicated that shortage area designation has little direct effect on indicators of access and use. Factors such as income and health insurance coverage appear to be more closely associated with access and use than is an area's designation as a HMSA. The assumptions concerning access to care in federally designated shortage areas should therefore be reexamined.

Demography↗
PubMed1982

The localization of vasotocin and neurophysin neurons in the diencephalon of the pigeon, Columba livia.

Vasotocin (VT)- and neurophysin (NP)-synthesizing neurons were demonstrated by immunocytochemistry in the diencephalon of the pigeon, Columba livia. Three diencephalic regions contain VT-NP cells: (1) periventricular preoptic area and hypothalamus, including nucleus periventricularis magnocellularis (PVM); (2) lateral preoptic area and hypothalamus; and (3) dorsal diencephalon. The immunoreactive cells in each of these three regions were divided into groups based on cytology and topography. No differences were found in the location of VT and NP cell groups. The periventricular region contains three continuous cell groups (P1-P3) extending from the posteroventral preoptic area to the anterodorsal hypothalamus and PVM. The lateral region has two cell groups composed of medium- to large-sized cells associated with the quintofrontal tract (L1) or with the optic tract (L2), while a third group (L3) lies between these two cell groups. Two accessory cell groups reside in the dorsolateral hypothalamus; L4 contains scattered cells of varied size, whereas L5 has small- to medium-sized cells clumped together. The dorsal diencephalic cell groups are found in the following locations: (1) lateral and dorsal to the lateral forebrain bundle (DD1); (2) in the area ventral to the dorsomedial anterior thalamic nucleus and dorsolateral to PVM (DD2); and (3) at the dorsolateral border of nucleus rotundus (DD3). To avoid potentially inaccurate mammalian homologies, the cell group nomenclature denotes topographic position. Nevertheless, the presence of VT-NP cells in PVM and projections to the brainstem and spinal cord suggest a homology between PVM and some of the parvocellular subnuclei of the mammalian paraventricular nucleus.

Animals↗
PubMed1982

Efferent connections of the lateral hypothalamic area of the rat: an autoradiographic investigation.

The efferent projections of the lateral hypothalamic area (LHA) at mid-tuberal levels were examined with the autoradiographic tracing method. Connections were observed to widespread regions of the brain, from the telencephalon to the medulla. Ascending fibers course through LHA and the lateral preoptic area and lie lateral to the diagonal band of Broca. Fibers sweep dorsally into the lateral septal nucleus, cingulum bundle and medial cortex. Although sparse injections are found to the ventromedial hypothalamic nucleus, a prominent pathway courses to the dorsal and medial parvocellular subnuclei of the paraventricular nucleus. Labeled fibers in the stria medullaris project to the lateral habenular nucleus. The central nucleus of the amygdala is encapsulated by fibers from the stria terminalis and the ventral amygdalofugal pathway. The substantia innominata, nucleus paraventricularis of the thalamus, and bed nucleus of the stria terminalis also receive LHA fibers. Three descending pathways course to the brainstem: (1) periventricular system, (2) central tegmental tract (CTT), and (3) medial forebrain bundle (MFB). Periventricular fibers travel to the ventral and lateral parts of the midbrain central gray, dorsal raphe nucleus, and laterodorsal tegmental nucleus of the pons. Dorsally coursing fibers of CTT enter the central tegmental field and the lateral and medial parabrachial nuclei. The intermediate and deep layers of the superior colliculus receive some fibers. Fibers from CTT leave the parabranchial region by descending in the ventrolateral pontine and medullary formation; some of these fibers sweep dorsomedially into the nucleus tractus solitarius, dorsal motor nucleus of the vagus, and nucleus commissuralis. From MFB, fibers descend into the ventral tegmental area and to the border of the median raphe and raphe magnus nuclei.

Amygdala↗
PubMed1982

Regular source of care and the minority aged.

Data from the National Medical Care Expenditure Survey are used to examine the access of elderly minorities to a regular source of medical care. The findings suggest that such elderly persons are about as likely as the white elderly to have a routine point of entry into the medical care system. There are, however, difference in the type of setting at which care is received. Compared with the elderly population of whites, the elderly population of minorities is more likely to have a regular source of care in an institutional setting and less likely to have a regular source of care that provides house calls or emergency services. The absence of a usual source of care may be a contributing factor to the difference in use of health services between the white and the nonwhite elderly populations.

Aged↗
PubMed1981

Efferent projections of the medial preoptic nucleus and medial hypothalamus in the pigeon.

The efferent projections of the medial preoptic nucleus (POM), anterior-medial hypothalamic area (AM), and the posteromedial hypothalamic nucleus (PMH) in the pigeon were traced by the autoradiographic technique. Similar and differential connections were noted from these regions. Projections from POM and AM-PMH were traced to nucleus septalis lateralis, nucleus dorsomedialis thalami, nucleus dorsolateralis anterior thalami (pars ventralis), posterior hypothalamic and medial mammillary areas, area ventralis tegmenti (Tsai), central gray of midbrain and nucleus intercollicularis and substantia grisea periventricularis of the midbrain. The density of silver grains in these regions differed with POM and AM-PMH injections. Other projections were observed exclusively from only one or two of the nuclear regions injected. Connections from POM and the rostral part of AM were seen to the median eminence, neurohypophysis, and the nucleus of anterior pallial commissure. Only cells of the anterior part of AM project fibers to nucleus septalis medialis. In the hypothalamus, projections from POM are concentrated in the periventricular region and in the preoptic-hypophyseal tract in the extreme lateral hypothalamus, while AM-PMH projections are heaviest in the medial hypothalamus and lateral preoptic area. A major difference in the connections of PMH from POM is the more substantial PMH projection to the midbrain. A prominent projection courses dorsolaterally and posteriorly from PMH toward nucleus ovoidalis and splits into two pathways: a lateral pathway which heavily innervates n. intercollicularis and the periventricular gray and a ventrolateral projection to the midbrain tegmentum. The projections described above provide anatomical substrates for neuroendocrine, autonomic, and behavioral functions.

Animals↗
PubMed1981

An autoradiographic determination of the efferent projections of the suprachiasmatic nucleus of the hypothalamus.

The efferent projections of the suprachiasmatic nucleus of the hypothalamus (SCN) have been investigated by the use of the anterograde autoradiographic technique. The majority of the fiber connections from SCN are to hypothalamic nuclei. The dorsal and periventricular parvocellular divisions of the paraventricular nucleus (PVN) and the medial part of the dorsomedial hypothalamic nucleus receive dense fiber projections. Also, fibers about the medial parvocellular division of PVN. Many descending fibers course into the retrochiasmatic area and pass to the ventral and medial borders of the ventromedial hypothalamic nucleus, as well as through the central zone of this nucleus. A few fibers at the lateral border of the ventromedial hypothalamic nucleus sweep dorsomedially into the posterior hypothalamic area and midbrain central gray. The major extrahypothalamic projection is to the periventricular thalamic nucleus.

Animals↗
PubMedDate not supplied

Access to care: how much difference does Medicaid make?

Using the 1994 Robert Wood Johnson Foundation National Access to Care Survey, we examine the likelihood of having a usual source of care, inability to obtain needed care, and number of physician visits for persons with private insurance, Medicaid coverage, and no insurance. Inability to obtain services is surprisingly consistent: For each service, Medicaid enrollees were about half as likely as uninsured persons and about twice as likely as privately insured persons were to report difficulty. For other access measures, access for those on Medicaid more closely resembles that of the privately insured than that of the uninsured.

Adult↗
PubMedDate not supplied

Health care use among undocumented Latino immigrants.

Using data from a 1996/1997 survey of undocumented Latino immigrants in four sites, we examine reasons for coming to the United States, use of health care services, and participation in government programs. We find that undocumented Latinos come to this country primarily for jobs. Their ambulatory health care use is low compared with that of all Latinos and all persons nationally, and their rates of hospitalization are comparable except for hospitalization for childbirth. Almost half of married undocumented Latinos have a child who is a U.S. citizen. Excluding undocumented immigrants from receiving government-funded health care services is unlikely to reduce the level of immigration and likely to affect the well-being of children who are U.S. citizens living in immigrant households.

Adolescent↗
PubMedDate not supplied

The concentration of health care expenditures, revisited.

In two previous publications, we described the distribution of health care expenditures among the civilian, noninstitutionalized U.S. population, specifically in terms of the share of aggregate expenditures accounted for by the top spenders in the distribution. Our focus revealed considerably skewed distribution, with a relatively small proportion of the population accounting for a large share of expenditures. In this paper we update our previous tabulations (last computed using data more than a decade old) with new data from the 1996 Medical Expenditure Panel Survey (MEPS). Our findings show that the skewed concentration of health care expenditures has remained very stable; 5 percent of the population accounts for the majority of health expenditures.

Age Factors↗