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Biomedical subjects

M Singer

Publications and source records attributed to M Singer.

At least 289 records · Page 16Linked to original sources
PubMed1977

Intraperitoneal transplants of taste buds in the newt.

Autografts of tongue onto the liver contained taste buds without nerves for up to 30 days. However, these denervated taste buds were generally smaller than normal and distorted in structure. Nerve fibers invaded the graft from the liver and after 30 days normal appearing taste buds were found only in implants of tongue which contained extensive nerve fibers. Thus it appears that certain visceral nerves can maintain and possibly induce taste bud formation in implants of tongue. This is interpreted as additional evidence for the trophic influence of nerves upon taste buds. Moreover, this ability to maintain taste buds is not restricted to gustatory nerves in the newt.

Animals↗
PubMed1977

Relation between nerve fiber number and pectoral fin regeneration in the teleost.

The number of nerve fibers per unit of amputation surface area has been determined in four teleosts capable of regenerating their fins (Gobius paganellus, Gobius minutus, Ictalurus nebulosus and Fundulus heteroclitus) and in two-non-regenerating ones (Cottus bubalis and Blennius pholis). The number of nerve fibers is about 16 in the non-regenerating fin and varies between 25 and 35 in the regenrating ones. These data, correlated with previous ones obtained on tetrapods, affirm the principle that there is a phylogenetic decline in the quantitative innervation of the vertebrate appendage. Moreover, they show that in the fish a quantitative neuronal threshold must also be satisfied in order for fin regeneration to occur. The threshold, in terms of fiber number, is higher than in the urodele amphibian. However, the fibers appear to be of smaller caliber; and so, the total amount of neuroplasm at the amputation surface which is required for regeneration may be similar to that for the amphibian.

Animals↗
PubMed1977

Neurotrophic stimulation of DNA synthesis in the regenerating forelimb of the newt, Triturus.

The effect of infusions of soluble newt brain extracts on deoxyribonucleic acid (DNA) synthesis in the denervated, regenerating newt blastema has been studied. When moderate early to early regenerates are denervated for 48 hours, DNA synthesis normally drops to about 40% of that found in contralateral, innervated blastemas. Infusion of brain extract halfway through the denervation period (at 24 hours) approximately doubles the rate of DNA synthesis in denervated regenerates.

Animals↗
PubMed1977

The effect of light on forelimb regeneration in the newt.

The forelimb of the newt, Triturus (Notophthalamus) viridescens, was bilaterally amputated and the animals subjected to different photoperiods during the period of regeneration, namely (1) continuous light, (2) 15 hours of light/day and (3) total darkness. Animals exposed to continuous light reached the palette regeneration stage four to five days before those kept in total darkness with the 15 hours of light/day animals being intermediate. The difference in regeneration rate was first evident in the moderate early stage (blastema accumulation stage); it then increased during subsequent stages and the difference persisted during the observation period. In an attempt to determine whether the retina was the receptor of light affected, some animals were blinded at the time of amputation and subjected to continuous light. Their rate of regeneration was similar to sighted animals subjected to continuous light but greater than sighted animals in total darkness. The pineal is discussed as the likely mediator of the photo effect.

Animals↗
PubMed1977

Diagnosis of a bleeding Meckel's diverticulum using radiopertechnetate.

A case report of bleeding from a Meckel's diverticulum diagnosed by Tc99-m pertechnetate scanning is presented. The noninvasive advantage of this method justifies its early use as a diagnostic measure when a Meckel's diverticulum is suspected in the differential diagnosis of lower gastrointestinal bleeding.

Adult↗
PubMed1977

Canine exocrine pancreatic secretory changes induced by an intragastric ethanol test meal.

In five dogs with chronic gastric fistulas (Thomas cannula) and a new type of chronic pancreatic fistula which permits collection of pure nonactivated pancreatic juice after ingestion of a test meal, the following series of experiments were performed: In the first series, a test meal (400 gm. canned dog meat) was given with 200 ml. saline simultaneously infused through the gastric cannula. In response to this stimulus, the 20-minute peak pancreatic flow rate and bicarbonate output were respectively 33% and 34%, of the maximal secretion of the pancreatic gland obtained with secretin in six control dogs provided with gastric and the classical Thomas duodenal fistula. The 20-minute peak protein output represented 84% of the maximal secretory capacity attained with dose-response curves to CCK in the same group of control animals. In the second series either 1.5 or 2.0 gm./kg. ethanol were given instead of saline. Intragastric ethanol induced a dissociation of pancreatic secretion: a significant inhibition of flow rate, of bicarbonate concentration and output and a significant rise of protein concentration; protein output remaining unchanged. It is postulated that ethanol, acting on the stomach and duodenojejunum, evokes, independently of its gastrin-releasing capacity, and unknown humoral or nervous mechanism that counteracts the ethanol-elicited cholinergic-mediated inhibition of pancreatic protein secretion which has been previously described.

Animals↗
PubMed1976

Synaptoid profiles in regenerating crustacean peripheral nerves.

Synapse-like structures occurring in regenerating crayfish peripheral nerves are characterized by aggregates of small (250 to 600 A) electron lucent vesicles adjacent to a thickened "presynaptic" membrane. Such synaptoid profiles are seen opposite other axons, glial processes or extracellular fibrous material. Junctions with cellular elements do not show "postsynaptic" specializations. These complexes are compared to axo-glial synapses in the developing spinal cord and to synaptoid configurations observed by others in vertebrate and invertebrate neurosecretory systems.

Animals↗
PubMed1976

Neurotrophic activity of brain extracts in forelimb regeneration of the urodele, Triturus.

The loss in protein synthesis which the regenerating forelimb of the newt suffers after denervation can be recovered by infusing into it an extract of newt soluble brain protein. Moreover, the synthesis of basic protein shows a greater response to the active brain principle than does that of acidic protein. The active agent of the nervous tissue is destroyed by heat and trypsin digestion. Extracts of liver and spleen, similarly prepared, do not evoke recovery of lost protein synthesis. Synaptosomal extracts of the frog brain also cause recovery of protein synthesis in the denervated regenerate, demonstrating the likelihood that the active agent is not species-specific within these amphibians, that it is a constituent of the neuronal fraction of nervous tissue, and that it is present in axonal terminals. Additional experiments showed that the nervous agent is likely a basic protein, and that the amount of protein infused is of the order of only 1.0% of the total regenerate protein. The significance of the findings is discussed in relation to the nature of the effect on protein synthesis and the nature of the active principle.

Animals↗
PubMed1976

Evidences for duodenopancreatic reflexes and an anti-CCK factor with lidocaine infused intravenously and sprayed topically on pancreatic papilla in nonalcoholic and alcohol-fed dogs.

In 14 duodenal Thomas fistula dogs, four of them alcohol-fed for two years, lidocaine, applied topically to the duodenal pancreatic papilla, inhibited secretin-induced pancreatic secretion probably by interrupting duodenopancreatic reflexes that contribute to the "pancreon's" cholinergic tone. Opposite effects were observed with lidocaine administered against a CCK plus secretin background stimulation of the pancreas. The significant rising of volume and protein output above plateau levels were enhanced by chronic alcohol feeding. Lidocaine infused intravenously did not change secretin-induced pancreatic secretion but raised CCK and secretin evoked plateau secretion levels. Chronic alcoholism enhanced these latter effects. Atropine perfusion superimposed on CCK and secretin stimulation did not prevent but raised the intravenous lidocaine-induced pancreatic secretion changes. It is postulated that the modifications elicited by lidocaine sprayed topically and infused intravenously on CCK plus secretin evoked pancreatic secretion plateau levels are due to depression of an anti-CCK factor secreted by the small intestine mucosa.

Administration, Topical↗
PubMed1975

[Endoscopic polypectomy of the upper gastro-intestinal tract: results and clinical features (author's transl)].

247 polyps were removed by electroresection through an endoscope (and 240 recovered) in 160 patients, aged 24-81 years. The histological substrate varied widely. Comparison of histological findings in the biopsy specimen with those of the entire polyp after polypectomy gave differing results in 41 of 87 gastric polyps. Complication rate of endoscopic polypectomy was 1.6%: postoperative bleeding occurred in three, which was treated conservatively, while in one patient ligation of a blood vessel by laparotomy became necessary. There were no perforation or lethal complications. Among three patients with hyperplasiogenic gastric polyps a "borderline lesion" was found in two (early carcinoma type I; adenocarcinoma). In 13 other patients with hyperplasiogenic polyps follow-up examination after one year revealed recurrence in three, absence of polyps in eight. In one patient a small gastric carcinoma (about 1 cm in diameter) was discovered four months later. It is possible that patients with hyperplasiogenic polyps are at a higher risk of cancer. Six-monthly endoscopic observation is, therefore, indicated.

Adenocarcinoma↗
PubMed1975

Distribution of ultrastructural tracers in crustacean axons.

Ruthenium red and horseradish peroxidase were used to compare the uptake of exogenous molecules into crayfish motor axons and their sheaths in severed and intact peripheral nerves. Both tracers penetrated the axonal sheath and were subsequently seen lining small vesicles and tubules in the axoplasm. Tracer appeared to enter the axon via pinocytotic vesicles. There were no perceptible quantitative or qualitative differences in ruthenium red uptake between intact and severed axons. However, counts of tracer-filled vesicles in axons exposed to peroxidase showed that at least three times as much tracer penetrated the severed as opposed to the intact axons.

Animals↗
PubMed1975

The interaction of histones with simian virus 40 supercoiled circular deoxyribonucleic acid in vitro.

The interaction of supercoiled, circular SV40 DNA with calf thymus histone fractions has been studied. Five- to ten-fold less f1 histone is required to complex a given amount of DNA compared to the other histones. When the supercoiled DNA is converted to either the relaxed circular form, or full length linear molecules, or gragmented linear or denatured stands, the efficiency of complex formation with f1 histone markedly decreases. We conclude that f1 histone has a special ability to interact with supercoiled DNA. This conclusion is supported by the fact that supercoiled circular Col E1 DNA interacts with f1 as efficiently as does SV40 DNA.

Animals↗