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Biomedical subjects

R Levin

Publications and source records attributed to R Levin.

At least 127 records · Page 7Linked to original sources
PubMed1976

Studies on phage internal proteins: formation of internal protein - T2 DNA complexes in vivo.

Internal proteins, synthesized in T2-infected Escherichia coli B cells were recovered from bacterial membranes during the early stages of infection. Approx. 15 min after the onset of infection, T2 and T4 internal proteins were released from the bacterial membranes and sedimented along with newly synthesized phage DNA. Internal protein-DNA complexes were also obtained by chromatography on hydroxylapatite columns. Internal proteins were not released from bacterial membranes after infection with amber mutants defective in genes 21, 22 and 23. It has been suggested that these complexes are intermediates in T-even phage morphogenesis.

Cell Membrane↗
PubMed1975

Maternal influences on ontogeny of suckling and feeding rhythms in the rat.

To assess the effects of both maternal and endogenous factors on the ontogeny of nocturnal feeding in the rat, day and night weight gain was determined in the sighted or blind litters of sighted or blind litters of sighted or blind dams and in young weaned at 15 days of age. Sighted dams impose a diurnal milk-intake pattern on their young. The nocturnal pattern of solid-food intake begins at 19 days of age. Blind litters also display nocturnal feeding when kept with sighted dams, but only until 35 days of age.

Age Factors↗
PubMed1975

Quantitative analysis of the rescue of RNA sequences by mammalian type C viruses.

The specificity and quantitation of the rescue of RNA sequences by mammalian type C viruses has been investigated. Type C virus can package with specificity only type C viral RNA. Type C viruses do not encapsidate with comparable efficiency either type B viral or cellular globin mRNA. Conversely, a non-type C mammalian retravirus, MP-MV, cannot encapsidate type C RNA. A revertant of Kirsten sarcoma virus (Ki-SV)-transformed nonproducer cells which fails to rescue biologically active Ki-SV after superinfection with helper virus had no detectable intracellular Ki-SV-specific RNA. The results suggest specific mechanisms by which type C viral proteins can package type C viral RNA and provide an approach to classifying RNA of potentially defective endogenous retraviruses as type C in origin.

Base Sequence↗
PubMed1975

Development of circadian periodicity in base and stress levels of corticosterone.

Base and stress levels of corticosterone were assessed at 4-h intervals over a 24-h period in male and female rats at age 18, 22, and 26 days. A significant periodicity in base levels of corticosterone is present at 22 days of age; however, a rhythm in stress values does not appear until age 26 days. At age 26 days the pattern of the circadian periodicity in both base and stress concentrations of corticosterone resembles that of the mature rhythm.

Animals↗
PubMed1975

Primary adenoid cystic carcinoma of the esophagus. Report of a case and review of the literature.

A case of primary adenoid cystic carcinoma of the esophagus is reported and a total of 15 cases was reviewed. There were 9 men, although earlier reports indicated the disease was more common in women. The lesion was located in the middle third of the esophagus in 10 cases. The possibility of tumor development from embryonal rests of the tracheobronchial tree in the esophagus is discussed. The prognosis of adenoid cystic carcinomas is not well known, but the treatment and prognosis appear similar to those of epidermoid carcinomas of the esophagus.

Aged↗
PubMed1969

Prolactin in the postpartum rat: synthesis and release in the absence of suckling stimulation.

Postpartum female rats deprived of suckling stimulation while being kept continuously with pups nonetheless suspended ovarian cyclicity for an average of 16 days and responded to uterine trauma by forming deciduomata. These results show that the extramammary stimulation afforded by young is alone capable of sustaining prolactin output from the adenohypophysis of the postpartum rat.

Animals↗
PubMedDate not supplied

The time course of creatine kinase elevation following concentric needle EMG.

The electromyographic (EMG) exam and creatine kinase (CK) are commonly used to evaluate patients with neuromuscular diseases. Prior studies have demonstrated minimal elevation of CK following monopolar needle examination, indicating that a false positive elevation does not occur in normal individuals. We studied the magnitude and time course of CK change resulting from concentric (CNEMG) and monopolar (MNEMG) needle EMG examination on healthy volunteers. CK increased in all subjects following CNEMG and MNEMG. Statistically significant mean CK elevations over baseline were observed at 4, 8, 12, and 24 hours for CNEMG and at 12 and 24 hours for MNEMG. Maximum elevation occurred at 12 and 24 hours for both CNEMG (mean, 178% of baseline) and MNEMG (mean, 134% of baseline). CK returned to baseline by 48 to 72 hours. In 25-30% of subjects CK elevation significantly exceeded the normal range. The magnitude of CK elevation is greater and the time course more prolonged than previously reported. CK measurements should be avoided 4 to 48 hours following CNEMG because of the potential for false positive results. Measurements immediately after and at 72 hours are not affected by the CNEMG or MNEMG. The time course for CK change following MNEMG is similar to CNEMG, but the magnitude is less.

Adult↗