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Biomedical subjects

M E Adams

Publications and source records attributed to M E Adams.

At least 145 records · Page 8Linked to original sources
PubMed1984

Metabolism of proctolin, a pentapeptide neurotransmitter in insects.

The in vitro metabolism of [tyrosyl-3, 5-3H]proctolin (H-Arg-Tyr-Leu-Pro-Thr-OH) was studied in the following tissues from the American cockroach, Periplaneta americana: proctodeum, midgut, hemolymph, brain, terminal ganglion, and coxal depressor muscles. In all tissues assayed, the Tyr-Leu bond is the primary cleavage site, but scission of the Arg-Tyr bond is also significant. Greater than 90% of the degradative activity is found in the 100,000 X g supernatant from homogenates. In vivo studies with the tobacco hornworm, Manduca sexta, show that topically applied proctolin does not penetrate larval cuticle; proctolin is readily degraded to constituent amino acids (at least to Tyr) upon ingestion.

Animals↗
PubMed1984

In vivo and in vitro stimulation of chondrocyte biosynthetic activity in early experimental osteoarthritis.

The biosynthesis of proteoglycans in the menisci and articular cartilages of the knee (stifle) of mature beagles was studied in the early stages of experimental osteoarthritis. The rate of proteoglycan synthesis, determined by systemic labeling in vivo at 21, 42, and 84 days after sectioning of the anterior cruciate ligament, was generally found to be 1.5-2.5-fold higher than control in articular cartilages and 3-10-fold higher than control in menisci. The medial meniscus was more stimulated than the lateral meniscus, and the medial tibial plateau under the meniscus was more stimulated than the adjacent tibial area. This area-specific stimulation suggests the involvement of mechanical factors in the cellular response. The rate of proteoglycan synthesis determined in vitro at 7, 14, and 21 days after operation was also about 2-fold higher than control in articular cartilages and about 3-fold higher in menisci. This increase in biosynthetic activity in vitro was confirmed by 35S-autoradiography and appeared to be due to general stimulation of existing chondrocytes, particularly in the middle and deep zones of the articular cartilage and throughout the meniscal cartilage. The rate of proteoglycan synthesis determined in vitro in cartilages from 2-week and 3-week sham operated joints was also increased relative to controls, suggesting that humoral as well as mechanical factors are involved in stimulating chondrocyte activity.

Animals↗
PubMed1984

Instrumentation of a tablet breaking-strength tester.

The instrumentation of a tablet breaking-strength tester, for the automatic recording of hardness values, is described. A comparison is made between a computerized hardness tester and another identical model hardness tester from the same manufacturer ("standard"). Three lots of placebo tablets at different hardness values were compared. No significant difference was observed between the computerized unit compared with the "standard" unit.

Computers↗
PubMed1983

Peptide cotransmitter at a neuromuscular junction.

The neuropeptide proctolin (H-Arg-Tyr-Leu-Pro-Thr-OH) is present in the nerve terminals of an identified slow skeletal motoneuron in the cockroach. Proctolin is released onto the target muscle, a coxal depressor, by neuron stimulation and by depolarization with potassium. The physiological action of the motoneuron suggests that proctolin acts as a cotransmitter. Proctolin and neural stimulation produce delayed and sustained contractile effects without muscle depolarization.

Action Potentials↗
PubMed1983

The glycosaminoglycans in menisci in experimental and natural osteoarthritis.

The glycosaminoglycans in the menisci of beagles 5--7 years old were analyzed at various times after osteoarthritis was induced by sectioning the anterior cruciate ligament of one knee; the unoperated knee served as control. In the first month after induction, there were signs of inflammation in the operated joint. After 1 week, the water content was elevated and the glycosaminoglycan content (per dry weight) was reduced. The content of keratan sulfate decreased more than that of chondroitin sulfate, but the hyaluronic acid content did not change consistently. The relative proportions of chondroitin-4-sulfate, chondroitin-6-sulfate, and dermatan sulfate remained unchanged. After 3--18 months, the glycosaminoglycan levels reverted to normal, and there was some evidence that after 15--18 months, they were elevated above normal. These results, together with results obtained from single examples of mild and severe osteoarthritis in working foxhounds, suggest that, in contrast to articular cartilage, the meniscus is capable of some regeneration in response to injury.

Animals↗
PubMed1983

Target tissue models: cartilage changes in experimental osteoarthritis in the dog.

Transection of the anterior cruciate ligament in the dog knee leads to a reproducible defined osteoarthritis (OA) with erosive cartilage loss, subchrondral sclerosis, and osteophyte formation, enabling studies of cartilage biochemistry before morphological changes are apparent. As early as 1 week after operation, menisci showed increased water content , 20% loss of galactosamine, and 40% loss of glucosamine. There was increased synthesis of larger proteoglycans (PG) at 3, 6, and 12 weeks, and the synthesis was greater in the menisci than the articular cartilage. there was no apparent impairment of the PG ability to aggregate with hyaluronate.

Animals↗
PubMed1982

Structural comparison of a homologous neuron in gryllid and acridid insects.

The fast extensor tibiae (FETi) motor neuron is responsible for exciting the extensor tibiae muscle to produce most of the force for jumping in acridids. Because of its relatively large size and crucial role in jumping, FETi has been studied in an ever-increasing number of orthopteran species. Here we describe the structure of the metathoracic FETi neuron in six species of acridids and in two species of gryllids. The morphology of FETi within the respective groups is essentially equivalent, but marked differences are apparent between acridid and gryllid FETis. There are similarities in the size and location of the cell body and the course of the neurite through the ganglion. Differences are found in the number of large branches, density of branching, and the volume of neuropil receiving branches. We propose that the gryllid FETi is an intermediate form between slow extensor tibiae motor neurons involved in walking and acridid fast extensor tibiae motor neurons specialized for jumping.

Animals↗
PubMed1982

Identification of proctolin-containing neurons.

Proctolin (H-Arg-Tyr-Leu-Pro-Thr-OH), a highly bioactive peptide found first in insects, is shown to be localized to specific neurons in the central nervous system (CNS) of the cockroach Periplaneta americana. Application of an antiproctolin serum to whole ganglia in a whole-mount immunohistochemical technique reveals the presence of proctolin immunoreactive neurons throughout the CNS. These neurons can be mapped and appear in consistent positions in different individuals. Some have been uniquely identified by intracellular dye injection combined with immunological localization. The presence of proctolin in individually identified neurons has been determined by high-pressure liquid chromatography combined with proctolin bioassay detection performed on extracts made from single identified cells. Some proctolin-containing neurons contain large vacuolelike inclusions in their cell bodies. These vacuoles appear to be the greatly enlarged lumena of the rough endoplasmic reticulum and may be part of the morphological substrate for the manufacture of proctolin. Electrophysiological studies suggest that some proctolin-containing neurons in different segmental ganglia, although not all, are normally recruited together as a functional unit by shared presynaptic input. This characterization of individual proctolin neurons is a prelude to a cellular study of the physiological role of a neuropeptide.

Animals↗
PubMed1981

The glycosaminoglycans of canine menisci.

The semilunar menisci of the knee have an important mechanical function and are commonly involved in joint degeneration. However, previously published analyses of the compositions of normal and degenerate human menisci vary widely. In the present study the glycosaminoglycan content and composition of selected areas of the menisci of eight normal knees of working foxhounds were determined. The menisci contained 10% less water and abut 8-fold less glucosaminoglycan than did the articular cartilage of these animals. Although the glycosaminoglycan composition was the same in different regions of the menisci, the total amounts varied considerably. Of the chondroitinase digestible material, approx. 60% was chondroitin 6-sulphate, 25% chondroitin 4-sulphate, 10% chondroitin and 5% dermatan sulphate. Hyaluronic acid accounted for about 6% of the total uronic acid.

Animals↗
PubMed1981

Pentapeptide (proctolin) associated with an identified neuron.

Individual neurons can be recognized and identified anatomically, physiologically, and biochemically in the insect central nervous system. Biochemical analyses of extracts prepared from one such identified neuron show it to be associated with a bioactive pentapeptide called proctolin. This peptide may be a neurotransmitter, and a preparation is established in which its physiological action can be studied at the cellular level.

Animals↗
PubMed1979

Transformed cells have lost control of ribosome number through their growth cycle.

Previous studies on the synthesis and function of the protein synthetic machinery through the growth cycle of normal cultured hamster embryo fibroblasts (HA) were extended here to a series of four different clonal lines of polyoma virus-transformed HA cells. Under our culture conditions, these transformed cells could enter a stationary phase characterized by no mitotic cells, very low rates of DNA synthesis, and arrest in a post-mitotic pre-DNA synthetic state. Cellular viability was initially high in stationary phase but, unlike normal cells, transformed cells slowly lost viability. The rate of protein synthesis in the stationary phase of the transformed cells fell to 25-30% of the exponential rate. Though this reduction was similar to that seen in normal cells, it was accomplished by different means. The specific reduction in the ribosome complement per cell to values below that of any cycling cell seen in normal cells, was not seen in any of the transformed lines. This observation, which implies a loss of normal control of ribisome synthesis through the growth cycle after transformation, was confirmed in normal Chinese hamster embryo fibroblasts and transformed CHO cell lines. Normal control of ribosome synthesis was restored in L-73 and LR-73, growth control revertants of one of the transformed CHO lines. The transformed lines reduced their protein synthetic rates in stationary phase either by a greater reduction in the proportion of functioning ribosomes than that seen in normal cells or by a decrease in the elongation rate of functioning ribosomes; the latter effect was not seen in the normal cells. A model for growth control of normal cells and its derangement in transformed cells is presented.

Animals↗