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Biomedical subjects

D Kahn

Publications and source records attributed to D Kahn.

At least 289 records · Page 16Linked to original sources
PubMed1984

On duration and smoothing rules in a demisyllable-based isolated-word recognition system.

In a recently proposed approach to isolated-word recognition, word reference templates are constructed from a universal set of demisyllable units by concatenating the appropriate demisyllables for each vocabulary item. A dynamic time warping (DTW) algorithm is used to align test and reference patterns optimally. Nevertheless some sort of syllable duration preadjustment is necessary because of the large potential difference in duration between isolated and in-context syllables. We have found that a simple rule that reduces the length of rhyme (final) demisyllables in nonword-final stressed syllables to approximately half their isolated-syllable duration provides recognition accuracy as high as that attained through use of complex, highly context-sensitive rules. In addition to its practical application, this result can be regarded as a further demonstration of the power of DTW. We have also investigated the requirements for parameter smoothing at demisyllable boundaries. We find that an optimal window duration for smoothing is about 60-90 ms, but that failure to smooth reduces recognition accuracy only about 2% in an 1109 word test set; that linear and parabolic smoothing are equally effective; and that it does not appear that recognition accuracy can be improved by smoothing in certain phonetic contexts only. Taken together, these results can be viewed as confirming the suitability of the demisyllable as the basic unit in recognition systems.

Humans↗
PubMed1984

Transhepatic changes in insulin and glucagon following partial hepatectomy in the pig.

In this study, glucose levels decreased after partial hepatectomy in the pig. This was associated with a decrease in insulin and an increase in glucagon levels. An added dextrose infusion resulted in hyperglycemia and appropriate responses in insulin and glucagon. Insulin clearance remained unchanged and glucagon extraction by the liver was decreased after partial hepatectomy. Changes in insulin and glucagon after partial hepatectomy appear to be related to the changes in blood glucose rather than the regenerative process.

Animals↗
PubMed1984

Endoscopic laser endarterectomy.

The effects of the Neodymium YAG laser on atheroma have been examined in human cadaver aortoiliac arteries and in normal porcine vessels. YAG laser is effective when used to ablate atheroma in an air environment and can be used successfully through the vascular endoscope. When atheroma were treated in the saline solution environment necessary for vascular endoscopy, the laser was less effective. Laser-treated areas of porcine arteries were not thrombogenic. Severe laser damage was easily recognized by blanching and marked elevation of the initma and consistently resulted in late aneurysm formation. ELE is feasible and further investigation is warranted.

Air↗
PubMed1983

Failure of repeated injection sclerotherapy to improve long-term survival after oesophageal variceal bleeding. A five-year prospective controlled clinical trial.

The role of sclerotherapy in long-term management after oesophageal variceal bleeding was assessed by comparing repeated sclerotherapy by means of a rigid oesophagoscope in 37 patients with control medical management in 38 patients. Varices were eradicated in 21 of the 22 patients analysed (95%) in the sclerotherapy group, but recurred in 13 of the 21 patients (average 21.5 months). Varices persisted in 13 of 14 surviving controls. The sclerotherapy patients had fewer recurrent bleeds than control patients (43 versus 73); the majority occurred before variceal eradication and were mild. However, there was no difference in survival in the two groups. The commonest cause of death was liver failure (37 patients). 32 complications occurred in 24 patients during 258 injections. Repeated sclerotherapy failed to improve survival in this trial, although varices were eradicated and recurrent variceal bleeds were prevented with adequate follow-up.

Acute Disease↗
PubMed1982

The stimulatory effect of a partially hepatectomized auxiliary graft upon the host liver. Observations on the regenerative response in orthotopic and heterotopic grafts.

Transplantation of an intact or partially hepatectomized auxiliary liver graft has been shown to result in a marked regenerative response (as measured by thymidine kinase activity and mitotic index) in the donor liver, apparently associated with rejection. This response was also transmitted to the host (portacaval-shunted) liver which showed a four- to sixfold increment in regenerative response. Livers transplanted by conventional orthotopic techniques also showed a marked regenerative response. The control groups of animals which were subjected to portacaval shunt, portacaval transposition or liver autografting showed a minimal regenerative response. The regenerative response after orthotopic transplantation is an original observation of great relevance to the overall response to liver grafting and may help partly to explain the variable responses to the procedure.

Animals↗
PubMed1982

Metabolic control of Klebsiella pneumoniae mRNA degradation by the availability of fixed nitrogen.

The chemical and functional stability of Klebsiella pneumoniae mRNAs was dependent on the nitrogen status of the organism. During exponential growth on N2 or NH+4 as N-source the half-lives of mRNAs were 10 and 4 min, respectively. When NH+4-grown cells were starved of NH+4 for 3 h, under which conditions the nitrogen fixation (nif) genes were derepressed, the half-life of mRNAs increased to 20 min. Addition of NH+4 to such N-starved suspensions rapidly destabilized mRNAs with a resultant half-life of 9 min. This destabilization occurred even in the presence of transcription inhibitors, which indicated metabolic control of mRNA degradation. Under most conditions studied the functional decay of nif-specific mRNAs paralleled the decay of bulk mRNAs.

Ammonium Sulfate↗
PubMed1982

Steroid treatment of pseudo-croup.

In a randomized, controlled investigation, 349 children with pseudo-croup stage I or II were given 6 mg of dexamethasone or placebo. Although the rate of recovery was similar in both groups, there was a significant difference when only the more seriously affected children were considered: steroid treated patients recovered quicker. Steroids appear to be useful in the routine treatment of simple, uncomplicated pseudo-croup, even if their effect apparently is not very impressive. Thus, close supervision remains the most important measure in this nearly always benign but potentially dangerous condition.

Acute Disease↗
PubMed1980

Analysis of regulation of Klebsiella pneumoniae nitrogen fixation (nif) gene cluster with gene fusions.

Gene fusions in which the lac genes are under the control of each promoter in the Klebsiella pneumoniae, nitrogen fixation (nif) gene cluster have been constructed. These fusions have been used to examine positive control of the cluster and the response of individual genes to repression by ammonia and oxygen. De-repression of nif transcriptional units is coordinate and molybdate is required for maximal expression of the structural gene operon, which is autogenously regulated.

Ammonia↗
PubMed1980

Neurotensin neurons in the rat hypothalamus: an immunocytochemical study.

Neurotensin was localized in the hypothalamic tissues of adult Sprague-Dawley rats by immunoperoxidase techniques. Visualization of perikarya was greatly enhanced by intraventricular administration of colchicine. Many perikarya containing neurotensin-like immunoreactivity were seen in the medial preoptic area, the periventricular hypothalamus, the parvocellular portion of the paraventricular nucleus, the arcuate nucleus, and the lateral hypothalamus in the perifornical area. There were moderate numbers of cell bodies in the ventral portion of the anterior hypothalamus, the dorsomedial nucleus, and the posterior hypothalamus. No positive cells were seen in the suprachiasmatic, ventromedial, or mammillary nuclei. Reactive fibers were generally distributed in the same regions as cell bodies. Additional dense collections were seen in the lateral part of the zona externa of the median eminence, the pituitary stalk, the posterior mammillary nucleus, and the most lateral portions of the hypothalamus at the medial edge of the crura cerbri. There were smaller numbers of fibers found in the pre-mammillary and posterior hypothalamic nuclei and the posterior pituitary gland. These results indicate that the neurotensin system in the hypothalamus is very extensive and complex, as it is in many other brain regions. Neurons and fibers are found in many hypothalamic areas, including projections to the hypophysial portal system in the median eminence, suggesting that neurotensin may affect neuroendocrine mechanisms at several levels, including the anterior pituitary gland.

Animals↗
PubMed1980

Thymidine kinase: an inexpensive index of liver regeneration in a large animal model.

Most studies of liver regeneration have been restricted to small animals because of the cost of assessment of DNA synthesis by the standard method of thymidine incorporation in vivo. This paper presents the use of thymidine kinase as an inexpensive measure of regeneration in large animals. The use of the large model is advantageous because of the availability of serial blood and tissue samples from the same animal. Initially, the responses in thymidine kinase and thymidine incorporation over a period of 96 hr were shown to correspond well in rats subjected to 68% and 34% hepatectomy. Any delays could be attributed to different times of operation. A reproducible technique for 50% partial hepatectomy in the pig was developed, and the animals were studied by daily open liver biopsy for 7 days. The responses in thymidine kinase activity and mitotic indices showed tha peak regeneration occurred at 3-4 days. Levels of aspartate amino transferase were elevated sevenfold after partial hepatectomy but returned to normal within 96 hr. The levels of alkaline phosphatase and bilirubin were unaltered, confirming that the biliary drainage had not been compromised. This study offers the pig as another suitable model for the study of liver regeneration and thymidine kinase activity as a suitable index.

Animals↗
PubMed1979

A prospective evaluation of injection sclerotherapy in the treatment of acute bleeding from esophageal varices.

In a 25 month study of massive upper-gastrointestinal hemorrhage, 64 patients were shown to have esophageal varices on emergency endoscopy. Twenty-four patients were actively bleeding from varices and were treated with a Sengstaken tube, and in 22 this was followed by emergency injection sclerotherapy using a rigid esophagoscope and general anesthesia. These 22 patients were followed prospectively and had 51 episodes of endoscopically proven active bleeding from esophageal varices which required Sengstaken tube control of hemorrhage during 36 separate admissions. This group included our total experience of injection sclerotherapy in acute variceal bleeding. The majority (14 of 22 patients) had alcoholic cirrhosis. Definitive control of variceal bleeding during the period of hospitalization was achieved in 33 hospital admissions (92%), usually with a single injection (27 hospital admissions: 75%). The results were satisfactory in 26 hospital admissions (72%). There were nine deaths (41% overall patient mortality rate), but no patient died primarily of variceal bleeding, and exsanguinating variceal bleeding was no longer a problem. The mortality rate per injection was 18%, and the mortality rate per hospital admission was 25%. Injection sclerotherapy is proposed as the emergency treatment of choice for patients with proven bleeding esophageal varices who do not stop bleeding on initial conservative treatment.

Acute Disease↗
PubMed1979

A prospective controlled trial of sclerotherapy in the long term management of patients after esophageal variceal bleeding.

The preliminary results of the first 25 months of a prospective randomized controlled clinical trial, designed to compare repeated injection sclerotherapy with conservative medical management in the long term treatment of all patients shown to have previously bled from esophageal varices, are presented in detail. To date, 31 patients have been randomized, 15 in the chronic injection group and 16 in the control medical management group. In addition, five patients excluded for geographic reasons have been injected out of trial. Ethanolamine oleate has been injected into the varices, using a modified rigid esophagoscope under general anesthesia. The preliminary results have been encouraging. It has been possible to eradicate esophageal varices in the chronic injection group and, once the varices had been eradicated, no patient had recurrence of variceal bleeding. On the other hand, recurrent variceal bleeds have remained a continuing problem in a number of the patients in the control study. A longer follow-up period will be required to assess both the quantitative and the qualitative aspects of survival and to determine how long esophageal varices will remain eradicated as well as how frequently repeated injections will be required.

Adolescent↗