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Biomedical subjects

B Kramer

Publications and source records attributed to B Kramer.

34 records · Page 2Linked to original sources
PubMed1987

A microprocessor system for the digital synthesis of pulsed and continuous discharges of electric fish (or animal vocalizations).

Traditionally, the sensitivity of electric fish to electric stimuli has been investigated using a variety of electronically generated signal functions, for example sine, square, and sawtooth waves (both continuous and pulsed). None of these resemble the species- or sex-specific electric organ discharges (EODs) of fish. Therefore, EODs recorded on magnetic tape were used in open-loop playback experiments. However, as shown in the present paper, the waveforms of EODs reproduced from magnetic tape are distorted, and cannot be manipulated with speed and accuracy as to frequency or pulse repetition rate by feedback from the experiment. Good EOD imitations are generated by our microprocessor-based system for the digital synthesis of EODs which is controlled by a small 'personal computer'. Digitized EOD samples edited by computer are output by the fast digital-to-analogue converter of the microprocessor system. This system was devised for the synthesis of pulse-type (discontinuous) and wave type (continuous) EODs with continuous, on-line frequency and amplitude control. The rate of digital synthesis is 500 kHz in pulse-type EODs, and 250-500 kHz in wave type EODs at 0.06-0.24 Hz frequency resolution, depending on the repetition frequency of the synthesized wave EOD. The present paper describes the steps in EOD synthesis, and indicates some applications which benefit from the playback of high-fidelity imitations of natural EODs at amplitudes and frequencies selected by the experimenter, or automatically controlled by feedback from the experiment in closed-loop applications.

Analog-Digital Conversion↗
PubMed1987

The effect of pancreatic mesenchyme on the differentiation of endocrine cells from gastric endoderm.

To determine whether mesenchyme plays a part in the differentiation of gut endocrine cells, proventricular endoderm from 4- to 5-day chick or quail embryos was associated with mesenchyme from the dorsal pancreatic bud of chick embryos of the same age. The combinations were grown on the chorioallantoic membranes of host chick embryos until they reached a total incubation age of 21 days. Proventricular or pancreatic endoderm of the appropriate age and species reassociated with its own mesenchyme provided the controls. Morphogenesis in the experimental grafts corresponded closely to that in proventricular controls, i.e. the pancreatic mesenchyme supported the development of proventricular glands from proventricular endoderm. Insulin, glucagon and somatostatin cells and cells with pancreatic polypeptide-like immunoreactivity differentiated in the pancreatic controls. The latter three endocrine cell types, together with neurotensin and bombesin/gastrin-releasing polypeptide (GRP) cells, developed in proventricular controls and experimental grafts. The proportions of the major types common to proventriculus and pancreas (somatostatin and glucagon cells) were in general similar when experimental grafts were compared with proventricular controls but different when experimental and pancreatic control grafts were compared. Hence pancreatic mesenchyme did not materially affect the proportions of these three cell types in experimental grafts, induced no specific pancreatic (insulin) cell type and allowed the differentiation of the characteristic proventricular endocrine cell types, neurotensin and bombesin/GRP cells. However, an important finding was a significant reduction in the proportion of bombesin/GRP cells, attributable in part to a decrease in their number and in part to an increase in the numbers of endocrine cells of the other types. This indicates that mesenchyme may well play a part in determining the regional specificity of populations of gut endocrine cells.

Animals↗
PubMed1986

Phase II evaluation of diaziquone in gastric and pancreatic cancers. A Southeastern Cancer Study Group Trial.

Seventeen patients with pancreatic carcinoma and 30 patients with gastric carcinoma were treated with diaziquone on days 1 and 8 of repeated 4-week courses. No objective responses were seen. Toxicity was primarily myelosuppression, nausea, and vomiting. Since only 10 chemotherapy-naive patients were treated in each disease category, we do not regard this as a definitive trial, but our experience suggests that this dose schedule is not likely to be useful in these types of cancer.

Aged↗
PubMed1985

Short course prophylactic cranial irradiation for small cell lung cancer.

Ninety-one patients with small cell carcinoma of the lung were given a shortened, intensive course of prophylactic cranial irradiation consisting of 2,000 rad in five fractions. The CNS relapse rate was 21%, but in only one of 91 patients was the brain the first and only site of relapse. Acute toxicities consisting of headache (16%) and nausea and vomiting (15%) were observed. Results are compared with previous results from other studies of cranial irradiation.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1985

Long-term effects of cancer chemotherapy.

As the management of advanced malignancy with multimodality therapy becomes more successful, the practicing general physician will see more chronic and late sequelae of therapy in the cured cancer patient. Chronic or late toxicities may occur in nearly every organ system. This article has briefly described the most common late toxicities that the practicing internist, pediatrician, family physician, and obstetrician/gynecologist should be prepared to recognize.

Adolescent↗
PubMed1979

An experimental investigation into the possible origin of pancreatic islet cells from rhombencephalic neurectoderm.

To determine whether or not any pancreatic islet cell type arises from rhombencephalic levels of neurectoderm, lengths of presumptive rhombencephalon (containing potential neural crest) of Black Australorp chick embryos at 6- to 9-somite stages were replaced isotopically and isochronically by neural tube of Japanese quail embryos. Some transplants included mesencephalic regions. In some cases various levels of the rhombencephalon were deleted and not replaced. The quail nuclear marker was detected in cranial ganglia in operated embryos sacrificed at 3 3/4 days of incubation and in enteric ganglia and cells accompanying some pancreatic nerves, in embryos killed at 7 days of incubation. This provided evidence of normal migration of crest cells from the grafts. Dopa was administered to the younger embryos, which were submitted to the formaldehyde-induced fluorescence procedure to demonstrate APUD (Amine Precursor Uptake and Decarboxylation) cells. No pancreatic APUD cells exhibited the quail nuclear marker. In 9- to 11-day embryos, A and B cells were identified by specific light and electron microscopic features. None showed the quail marker. The marker was also absent from those D cells seen and from cells of an as yet unidentified type, but not enough of these were found to warrant a conclusion. All islet cell types were found in embryos from which various levels of the rhombencephalon had been deleted. It is concluded that at least A and B islet cells are not derived from the rhombencephalic neurectoderm and probably not from mesencephalic levels. Their most likely origin remains the endoderm, which was the accepted source until recently.

APUD Cells↗
PubMed1978

An unusual case of persistent renal collar in a human adult male.

There are relatively few reports in the literature on accessory renal veins, and particularly that anomaly described as a persistent renal collar. The present paper describes a case in which a left renal vein is encountered in a human adult, both anterior and posterior to the abdominal aorta, though without a persistent left inferior vena cava.

Adult↗