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Biomedical subjects

D Smith

Publications and source records attributed to D Smith.

At least 1,171 records · Page 65Linked to original sources
PubMed1978

Conformation of [Leu5]enkephalin from X-ray diffraction: features important for recognition at opiate receptor.

The conformation of [Leu5]enkephalin is produced by a Tyr-Gly-Gly-Phe beta bend stabilized by antiparallel hydrogen bonding between tyrosine and phenylalanine. On the basis of a comparison of the observed structure with the structure of known opiate agonists, three hydrophilic and two hydrophobic regions have been identified as contributing to the recognition of the molecule at the opiate receptor site.

Endorphins↗
PubMed1978

Spontaneous resolution of severe aplastic anemia associated with viral hepatitis A in a 6-year-old child.

Recovery from acquired aplastic anemia associated with hepatitis is rare. This case of a 6-year-old boy with severe aplastic anemia is the first reported association of this disease with a hepatitis A infection. Antibody to hepatitis A (anti-HA) was not detected on admission, but was detected three weeks later. Infection with hepatitis B virus, cytomegalovirus (CMV), and Epstein-Barr virus (EBV) were excluded. The peak titer of anti-HA was higher than would be expected for passive transfer of antibody resulting from transfusions. The persistence of antibody for more than 20 months after the last transfusion was not consistent with passive antibody, which would be expected to disappear over that time. This child had indications for allogeneic marrow transplant and a sibling donor who was histocompatible. However, the transplant was postponed because the prognosis was considered to be poor in the presence of active hepatitis. There was a spontaneous remission without the necessity of the transplantation procedure.

Anemia, Aplastic↗
PubMed1978

Current-to-voltage convertor for measurement of oxygen.

A highly sensitive, miniature, inexpensive circuit for the measurement of PO2 in vivo has been described. The circuit is constructed from a current-to-voltage convertor, clamping circuit, differential amplifier, and reverse voltage and overvoltage protector. The design of the circuit allows us to apply voltage bias to the measuring electrode while grounding the preparation. The clamping circuit holds the selected bias voltage constant while the differential amplifier subtracts this bias potential from the PO2 signal yielding an output voltage that is proportional to the current sensed by the oxygen electrode. The circuit is protected from reverse voltage and overvoltage.

Electronics↗
PubMed1978

An infertility data registry.

A computerized infertility data registry form has been developed in order to facilitate the storage of a large amount of reproductive data to allow subsequent analyses pertinent to the managment of the infertile couple. This abstract form of the patients' medical records had been readily applied to computer analysis using the SPSS reporting system. The abstract can be utilized both for the facilitation of patient management and as a means for obtaining a standardized, objective, retrospective review of clinical data. Through the evaluation and standardization of the therapeutic techniques frequently utilized by physicians, the treatment of infertile couples should be improved. Such an approach is essential for anyone involved in today's health care system.

Female↗
PubMed1977

Membrane-dependent cleavage of the human placental lactogen precursor to its native form in ascites cell-free extracts.

Messenger RNA derived from term placenta directs the synthesis of a precursor to human placental lactogen (prelactogen, molecular weight 25000) in an ascites cell-free system containing ribosome free supernatant and preincubated purified ribosomes. The processing of prelactogen to native lactogen (molecular weight 22200) was only observed when a microsomal membrane preparation was added prior to the synthesis of complete protein, i.e. before release. Placental mRNA directed the synthesis of prelactogen in asystem containing free polysomes, whereas in a comparable system containing membrane-bound polysomes both prelactogen and lactogen were synthesized. The prelactogen synthesized in the latter system could be cleaved by the addition of membranes at the start of incubation. Preprotein cleavage activity was inhibited 100% by 0.04% Tritonx-100, while protein synthesis was inhibited only about 30%. Using Triton to block cleavage specifically at intervals after mRNA and membrane additions, it was determined that the overall cleavage reaction required about 15 min. When the ascites system was incubated with charged initiator [35S]methionyl-tRNAfMet prelactogen was formed. The labeled prelactogen was processed when membranes were added after 60 min of incubation. The results indicate that prelactogen is the primary gene product, and cleavage activity is apparently associated only with the membrane-bound ribosomal fraction of the cell.

Animals↗
PubMed1977

Conformational alteration of protein synthesis elongation factor EF-Tu by EF-Ts and by kirromycin.

Alterations of the structure of EF-Tu have been investigated by using the rate of EF-Tu cleavage by trypsin as a conformational probe. The presence of EF-Ts bound to EF-Tu results in a 10-fold increase in the cleavage rate. The antibiotic kirromycin, which inhibits protein synthesis by virtue of its interaction with EF-Tu, mimics this effect of EF-Ts. Both kirromycin and EF-Ts also facilitate the exchange of free GDP with GDP bound to EF-Tu. The results suggest that EF-Ts and kirromycin induce a similar conformational change in EF-Tu, thereby "opening" the guanine nucleotide binding site. The trypsin-cleaved EF-Tu still can bind GDP and EF-Ts and can function in Qbeta replicase, but it no longer spontaneously renatures following denaturation in urea.

Anti-Bacterial Agents↗
PubMed1977

Variation in enterotoxigenicity of Escherichia coli.

The possibility that the variable severity of diarrheal disease due to enterotoxigenic Escherichia coli might be explained by quantitative differences in the activity of heat-labile enterotoxin was examined. The amount of toxin secreted by 13 enteropathogenic strains of E. coli was quantitated by measurements of the toxin-dependent increase in adenosine 3':5'-cyclic phosphate (cyclic AMP) in Chinese hamster ovary cells. The activity ranged from 150 pmol of cyclic AMP/ml per mg of protein to 4,040 pmol/ml per mg. With three representative strains there was good correlation (r = -0.999; P less than 0.05) between the amounts of cyclic AMP accumulated intracellularly (4,040, 2,071, and 470 pmol of cyclic AMP/ml per mg of protein) and the ability of the filtrate to distend the rabbit ileal loop, as measured by the amounts of toxin required to produce half-maximal distension (50% effective dose, which had values of 11.5, 27.5, and 38.5 mg, respectively). The observed strain-to-strain variation in toxin activity may explain the variation in severity of diarrheal disease caused by enterotoxigenic E. coli.

Animals↗