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Biomedical subjects

M L Schmidt

Publications and source records attributed to M L Schmidt.

At least 91 records · Page 5Linked to original sources
PubMed1985

Immunoblot analysis of horseradish peroxidase conjugates of wheat germ agglutinin before and after retrograde transport in the rat peripheral nervous system.

Immunoblot studies were performed on tissue extracts of rats injected with horseradish peroxidase (HRP) conjugates of wheat germ agglutinin (WGA) using anti-HRP and anti-WGA antisera. Immunoblots of uninjected, purified conjugates (WGA-HRP) demonstrated a 62-kilodalton (kd) conjugate (monomeric WGA conjugated to HRP). Other prominent immunobands included HRP (40 kd), monomeric WGA (22 kd), and 15- to 30-kd HRP breakdown products. Following injections of WGA-HRP into the submandibular gland of rats which survived 16 hr to 8 days, immunoblots were performed on homogenates of injected submandibular glands and of superior cervical ganglia containing neurons retrogradely labeled with WGA-HRP. The anti-HRP antiserum detected unconjugated, 40-kd HRP and a 62-kd immunoband corresponding to WGA-HRP in the superior cervical ganglia and submandibular glands. No immunobands were detected with the antiserum to WGA in superior cervical ganglia homogenates. Blots of submandibular gland homogenates harvested 24 hr after a WGA-HRP injection, but not at later time points, contained an immunoband reactive with the anti-WGA antiserum; it corresponded to monomeric WGA. These studies analyze for the first time the molecular composition of WGA-HRP conjugates before and after retrograde transport; they provide a novel approach for probing the intraneuronal transport and degradation of proteins. We conclude that morphologically defined endocytic pathways using protein markers reflect the endocytosis and transport of immunochemically altered and unaltered forms of the markers.

Animals↗
PubMed1985

Vitamin A deprivation in hamsters. Correlations between tracheal epithelial morphology and serum/tissue levels of vitamin A.

The effects of vitamin A deprivation on the tracheal epithelium of young hamsters were investigated. Colchicine was administered 6 h prior to death to induce metaphase arrest, thus making it possible to quantify the mitotic rates of basal cells and secretory (mucous) cells in the epithelium. Blood samples were taken from all hamsters, and liver samples from some, in order to measure serum and tissue levels of vitamin A. Age-matched controls were compared with the following groups of hamsters maintained on a vitamin A deficient diet: pre weight plateau animals (those gaining weight), weight plateau-early weight loss animals (those maintaining approximately the same weight for 3 or 4 days, followed in some cases by a loss of weight for 3 or 4 days), and prolonged weight loss animals (those showing a loss of weight for 5 or more days). Four week old hamsters in a pre weight plateau had undetectable amounts of vitamin A in their livers and declining levels in their serum, whereas 4 1/2 week old hamsters still gaining weight had barely detectable levels of vitamin A in their serum. Nevertheless, the tracheal epithelium of these animals was not different from controls in appearance, proportions of different cell types, mitotic rates of secretory and basal cells, or in the number of cells per millimeter of basement membrane (cell density). Vitamin A was undetectable in the serum and livers of hamsters in the weight plateau-early weight loss stage. At this time the tracheal epithelium showed minimal morphological change, with small focal areas of epidermoid metaplasia in some animals. The tracheas of animals in early weight loss were smaller than tracheas in the control group, and there was a trend towards an increase in the number of epithelial cells per millimeter basement membrane. Cell types in the minimally changed epithelium appeared nearly normal, but there was an increase in the proportion of basal cells, and an absence (or near absence) of division in both basal and secretory cells. Tracheal rings from hamsters in the prolonged weight loss stage were lined by a cornifying metaplastic epidermoid epithelium. Our findings demonstrate that barely detectable levels of vitamin A in the serum are sufficient to maintain normal growth and differentiation of hamster tracheal epithelium (late pre weight plateau stage). When vitamin A serum levels fall below detectable limits the animals enter the weight plateau-early weight loss stage. This stage is accompanied by an inhibition of tracheal epithelial cell growth, although nearly normal cellular differentiation is maintained.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Interneuronal transfer of axonally transported proteins: studies with HRP and HRP conjugates of wheat germ agglutinin, cholera toxin and the B subunit of cholera toxin.

Experiments in the visual system and the tongue-hypoglossal nucleus pathway of the rat with HRP and HRP conjugates of wheat germ agglutinin (WGHRP), cholera toxin (CTHRP) and the B subunit of cholera toxin (BHRP) were conducted to study the interneuronal transfer of proteins. Native HRP did not undergo such transfer. Intravitreal injections of WGHRP, CTHRP or BHRP all resulted in interneuronal transfer in the visual system, but there was no evidence for this in the tongue-hypoglossal nucleus pathway. Interneuronal transfer may: (1) require a ligand-cell surface interaction; and (2) occur only after the endocytosis and/or exocytosis of these conjugates at specific sites along the neuronal plasma membrane.

Animals↗
PubMed1980

A quantitative study of the occurrence and distribution of cytoplasmic laminated bodies in the lateral geniculate nucleus of the normal adult cat.

The proportion of neurons containing cytoplasmic laminated bodies (CLB) in the dorsal lateral geniculate nucleus (dLGN) of normal cats was determined by using a new method which permitted examination of large areas of this nucleus. Near the medial border of the dLGN (projection of the area centralis) in the A-laminae 30--60% of the neurons contain CLBs. Within the same region in lamina B only 10--30% of the nerve cells contain CLBs. In the monocular segment (MS) of lamina A 27--48% of the nerve cells contain CLBs. In the medial interlaminar nucleus (MIN) 25% of the neurons contain CLBs; these cells were distributed throughout the medio-lateral extent of the MIN. CLBs were also observed in neurons of the perigeniculate nucleus (PN) and in nerve cells embedded in the fiber sheet separating the dLGN from the pulvinar complex. The distribution of cells containing CLBs is extremely variable in all portions of the dLGN studied. The data presented in this paper indicate that CLB-containing cells in the dLGN may not be X-cells, as has been suggested by LeVay and Ferster ('77) because: (1) the distribution of neurons containing CLBs in lamina A does not match the distribution of X-cells recorded in this lamina; (2) some nerve cells in the MIN contain CLBs but very few X-cells have been found in this region.

Animals↗
PubMed1979

Groups for bereaved parents-how they can help.

The authors wished to establish an organized approach for helping parents of patients who had died. Over a 14-month period, 81 people participated in a series of groups. A closed-group, eight-meeting format was used, under professional leadership. Main topics covered in discussion were: problems and feelings associated with the death of the child; problems of coping with everyday life; and philosophical issues. Conclusions emphasize the need for professional leadership and screening of potential members. The groups were found to be an effective way to help normal people with normal grief. Participants saw their experience as extremely valuable, and as something which could not be gained through conventional therapy.

Adaptation, Psychological↗
PubMed1973

A search for the epidemic typhus agent in Ethiopian ticks.

The presence of antibodies to Rickettsia prowazeki in domestic animals from several parts of Africa, and the isolation of this rickettsia from the blood of goats and sheep and from ticks off cattle or camels in Ethiopia, led to the hypothesis that R. prowazeki in nature may occur in an extrahuman cycle involving ticks and domestic animals. This study attempted to recover R. prowazeki from 2 624 ticks (4 genera, 10 species) collected in central and southern Ethiopia. The ticks were examined by the haemolymph test and by the injection of tissues into guineapigs. No strains of typhus rickettsia were received and there was no serologic evidence suggesting the presence of this agent in any of the ticks examined. One Amblyomma cohaerens contained an organism that reacted specifically with fluorescing antibodies against R. prowazeki; attempts to isolate and identify this agent failed. Fifty-seven (2.2%) Amblyomma ticks (26 A. gemma, 17 A. variegatum, 14 A. cohaerens) were infected with rickettsiae of the spotted fever group, and probably represented R. conori or closely related rickettsial agents.

Animals↗