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Biomedical subjects

F Lang

Publications and source records attributed to F Lang.

At least 505 records · Page 28Linked to original sources
PubMed1977

Development of the dimorphic claw closer muscles of the lobster Homarus americanus: L Regional distribution of muscle fiber types in adults.

1. The closer muscles of the dimorphic claws (chelipeds) were studied for the presence and location of fast and slow muscle fibers. 2. Cutter claws were composed of about 60-70% short sarcomere (less than 4 mum) fast fibers; the remainder was longer sarcomere (greater than 6 mum) slow and intermediate (4-6 mum) fibers. 3. Crusher claws were composed of a uniform population of long sarcomere (6-13 mum) slow and intermediate (4-6 mum) fibers. 4. There was a regional distribution of fibers in the cutter claw. Ventral fibers were predominantly slow. Dorsal fibers and central medial fibers were fast. Proximal and distal fibers in the medial section were usually mixed. 5. The regional distribution of cutter fibers correlates with previous physiological studies on the distribution of the fast and slow motor axons to these muscle fibers.

Animals↗
PubMed1976

Growth of lobster giant axons: correlation between conduction velocity and axon diameter.

The conduction velocity and axon diameter of medial and lateral giant axons in lobsters was followed during growth from early juvenile (13 mm) to adult (250 mm) forms. In both axons, conduction velocity increased more than 4-fold in the growth period examined. Correlated with the increase in conduction velocity is an increase in axon diameter and the relationship between these two parameters is expressed by the equation CV = krX, where X equals 0.5 for the lateral and 0.7 for the medial giant axons. The sheath surrounding the giant axons also increases in size during growth with that of the medial giant axon being considerably thicker than that of the lateral giant axon. The significance of the increase in axon diameters is to increase conduction velocity and thereby reduce the latency of the escape response mediated by these giant axons.

Animals↗
PubMed1975

Handling of allantoin by the rat kidney. Clearance and micropuncture data.

Renal excretion of allantoin was measured by tracer techniques. After injection of 2-C14 urate and H3 inulin, clearances of allantoin and inulin were measured and both proximal and distal tubules were micropunctured. In confirmation of earlier results 2-C14 urate injected into an intact animal is very rapidly converted to C14 allantoin: after 15 min more than 90% of urinary tracer is present as allantoin. It was further observed that 1) allantoin clearance is essentially identical with inulin clearance over a wide range of urine flows; 2) no net transport of allantoin occurs in either proximal or distal tubules. Clearly allantoin is handled by the rat kidney like inulin. The total excretion of filtered allantoin unlike that of filtered urate provides an easy and effective mechanisms for animals possessing the enzyme uricase to dispose of their purine loads.

Allantoin↗
PubMed1975

[A case of carcinoma of the stomach with calcification (author's transl)].

The authors found only 25 cases of calcified carcinoma of the stomach in the literature. The course in this case was rapidly fatal. Calcification within the tumour infiltrates the gastric wall and has a very characteristic miliary appearance, permitting one to make the diagnosis on a straight X-Ray of the abdomen. The mechanism of precipitation of calcium within certain mucus-secreting carcinomas has not been determined. Various theories are suggested.

Adenocarcinoma, Mucinous↗
PubMed1973

Synaptic differentiation in a regenerating crab-limb muscle.

Properties of synapses on regenerating nerve terminals of the single excitatory axon to the stretcher muscle were studied in the regenerating second walking leg of the shore crab, Grapsus. In the adult condition these synapses vary in physiological properties, ranging from high release, poorly facilitating types to low release, highly facilitating types. Synapses on regenerating stretcher-muscle fibers show a distinct temporal pattern of differentiation. In early limb buds, a characteristic fluctuating, excitatory postsynaptic potential, punctuated by failures of transmission, is seen, indicating a developmentally "naive" synapse with low quantal content. In these early stages proportionately more synapses are of the poorly facilitating type; the highly facilitating synapses appear increasingly in later stages. Thus, the type of synapse that will form seems likely to be related to the time of innervation. Synapses of early developmental stages found by electron microscopy are significantly smaller than those seen in adult muscles; thus, the synaptic contact area must increase during development. We postulate that contacts formed by the primary branches of the axon early in development differentiate into relatively large, poorly facilitating synapses, while contacts formed by secondary branches slightly later in development differentiate into smaller, highly facilitating synapses.

Animals↗
PubMed1973

Differential responses of crab neuromuscular synapses to cesium ion.

Excitatory postsynaptic potentials (EPSP's) generated in crab muscle fibers by a single motor axon, differ in amplitude and facilitation. Some EPSP's are large at low frequencies of stimulation and show little facilitation; others are smaller and show pronounced facilitation. When K(+) is replaced by Cs(+) in the physiological solution, all EPSP's increase in amplitude, but small EPSP's increase proportionately more than large ones. Quantal content of transmission, determined by external recording at single synaptic regions, undergoes a much larger increase at facilitating synapses. The increase in quantal content of transmission is attributable to prolongation of the nerve terminal action potential in Cs(+). After 1-2 h of Cs(+) treatment, defacilitation of synaptic potentials occurs at synapses which initially showed facilitation. This indicates that Cs(+) treatment drastically increases the fraction of the "immediately available" transmitter store released by each nerve impulse, especially at terminals with facilitating synapses. It is proposed that facilitating synapses normally release less of the "immediately available" store of transmitter than poorly facilitating synapses. Possible reasons for this difference in performance are discussed.

Action Potentials↗
PubMed1972

Synaptic vesicles: selective depletion in crayfish excitatory and inhibitory axons.

Stimulation of the excitatory axon of the opener muscle of the crayfish in the presence of the metabolic inhibitor 2,4-dinitrophenol leads to depletion of synaptic vesicles in nerve terminals containing round vesicles. Stimulation of the inhibitory axon under these conditions produces depletion of vesicles in other nerve terminals containing more elongate synaptic vesicles. The experiments show that terminals with round synaptic vesicles are excitatory and that terminals with elongate synaptic vesicles are inhibitory. Replenishment of synaptic vesicles appears to require metabolic energy.

Animals↗