Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.
Example: Abstract: Some patients converted from ventricular fibrillation to organized rhythms by defibrillation - trained ambulance technicians(EMT - Ds) will refibrillate before hospital arrival.The authors analyzed 271 cases of ventricular fibrillation managed by EMT - Ds working without paramedic back - up.Of 111 patients initially converted to organized rhythms, 19(17 % ) refibrillated, 11(58 % ) of whom were reconverted to perfusing rhythms, including nine of 11(82 % ) who had spontaneous pulses prior to refibrillation.Among patients initially converted to organized rhythms, hospital admission rates were lower for patients who refibrillated than for patients who did not(53 % versus 76 % , P = NS), although discharge rates were virtually identical(37 % and 35 % , respectively).Scene - to - hospital transport times were not predictively associated with either the frequency of refibrillation or patient outcome.Defibrillation - trained EMTs can effectively manage refibrillation with additional shocks and are not at a significant disadvantage when paramedic back - up is not available.
Example solution: Ventricular Fibrillation
Example explanation: This term is directly present in the abstract and it is one of the main topic in it. So can be chosen as the medical subject heading.

Problem: Abstract: We have determined the structures of high mannose (Man) oligosaccharide units of the alpha- and beta-subunits of mouse TSH heterodimers and of free alpha-subunits. Mouse thyrotropic tumor tissue, or pituitaries from euthyroid or hypothyroid mice, were incubated with D-[2-3H]Man, homogenized, and incubated in the presence or absence of pH 3 buffer to dissociate heterodimers. Highly enriched TSH beta-subunits, or TSH heterodimers, were obtained using anti-TSH beta serum and free alpha-subunits were subsequently obtained using anti-LH alpha-serum. High Man units released by endoglycosidase H were analyzed by paper chromatography. At 1 and 3 h oligosaccharides with 8 or 9 Man residues predominated in all subunits. In all three tissue types, units with 9 Man tended to accumulate in TSH beta-subunits, whereas Man-trimming from Man9GlcNAc to Man8GlcNAc proceeded more rapidly in TSH alpha-subunits, and in free alpha-subunits. The rate of TSH beta-subunit processing was also a function of tissue type; the rate in euthyroid pituitary tissue equaled that in tumor tissue and was greater than that in hypothyroid pituitary tissue, suggesting that processing may be physiologically regulated. Hypothyroid calf serum slowed TSH alpha-subunit processing in euthyroid pituitaries. Thus, the previously reported slower processing of Man9GlcNAc to Man8GlcNAc in heterodimers as compared to free alpha-subunits is in large part due to accumulation of Man9GlcNAc in TSH beta-subunits.
Solution: Animal