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Biomedical subjects

S Berger

Publications and source records attributed to S Berger.

At least 325 records · Page 18Linked to original sources
PubMed1978

Alternating polarity in rRNA genes.

Spread nucleolar material from A. exigua exhibits an unusual arrangement of rDNA cistrons. The cistrons form head-to-head "diamond-shaped" doublets with a short spacer separating the members of the doublet. Single cistrons are usually terminal and arrange tail-to-tail with the adjacent doublet, suggesting the possibility of a repeating unit with a tail-to-tail, "bow-tie" doublet configuration in which the cistrons (average length: 1.44 micron) could be explained by an extraordinary shrinking of the DNA strand during transcription. This suggestion is supported by the estimation of the molecular mass of an early, or the primary, transcription product (2.2 X 10(6)).

Acetabularia↗
PubMed1978

Protoplasts from Acetabularia: isolation and fusion.

Protoplasts were isolated from cells of Acetabularia cliftonii, which are presumed to be haploid. The release of the protoplasts occurred after treatment of the cells with papain or proteinase K. They are genuine protoplasts since they contain a nucleus. Fusion was initiated by mechanically pushing together two protoplasts. Under these conditions, the efficiency of fusion was more than 90% within 30 minutes at room temperature. Haploid cells from one cyst, i.e., cells which eventually would have formed gametes of the same mating type, exhibit a greater propensity for fusion as compared to haploid cells from different cysts.

Acetabularia↗
PubMed1976

Comparative pharmacokinetics of cefamandole, cephapirin, and cephalothin in healthy subjects and effect of repeated dosing.

Cefamandole nafate, cephapirin, and cephalothin were administered intravenously in crossover fashion to 12 volunteers, in dosages of 2 g every 6 h for 16 doses. Mean peak levels of cefamandole were approximately 50% higher than those of the other agents. The serum concentration curves appeared to decline bi-exponentially, suggesting that a two-compartment model was most applicable for pharmacokinetic analysis; accordingly, the t((1/2)) of cefamandole was significantly longer when the serum peak was omitted from the analysis (0.86 versus 0.73 h, P < 0.05). The half-lives of cephalothin and cephapirin, 0.34 and 0.36 h, respectively, were probably underestimates reflecting the inclusion of distribution-phase values in the calculation. Repeated dosing had no effect on the peak serum levels, half-life, serum clearance, or apparent volume of distribution with one exception: peak serum levels of cephapirin were significantly lower after the sixteenth than after the first dose. Marked variations within a given subject were noted in the half-life and apparent volume of distribution of cefamandole in several instances. Renal clearances of cefamandole exhibited saturation kinetics similar to those of penicillin G.

Cephalosporins↗
PubMed1976

Comparative incidence of phlebitis due to buffered cephalothin, cephapirin, and cefamandole.

Buffered cephalothin, cefamandole, and cephapirin were compared with respect to their tendency to produce phlebitis. Two grams of each agent was administered every 6 h for 4 days to 12 healthy volunteers in a double-blind crossover fashion. Approximately 50% of intravenous sites developed mild (grade 1) phlebitis and 25% developed moderate (grade 2) phlebitis. The frequency of grade 1 inflammation did not differ significantly among the three cephalosporins. The proportion of individuals eventually exhibiting grade 2 phelebitis was highest with cefamandole, lowest with cephalothin (P = 0.07), and intermediate with cephapirin; however, cephapirin required a substantially greater number of doses to produce grade 2 phelebitis than did the other two drugs. These findings, together with the results of other reports, suggest that interpretation of the phlebitogenic potential of these antibiotics must be made with caution.

Adolescent↗
PubMed1976

Activity of cefamandole and other cephalosporins against aerobic and anaerobic bacteria.

The activity of cefamandole was comparable to that of cephalothin, cefazolin, and cephaloridine against Staphylococcus aureus, Streptococcus pyogenes, and Diplococcus pneumoniae. In contrast, cefamandole was considerably more active than cephalothin, cefazolin, or cephaloridine against gram-negative facultative bacilli, including Haemophilus influenzae, the most striking disparities being noted with indole-positive Proteus and Enterobacter. Bacteroides fragilis was more susceptible to cefoxitin than to cefamandole or cefazolin (median minimal inhibitory concentration, approximately 8, 32, and 32 mug/ml, respectively); cephalothin exhibited still less activity against this species. The majority of other anaerobes were inhibited by relatively low concentrations of all four cephalosporins. The results indicate a potentially valuable role for cefamandole against facultative gram-negative bacilli, including H. influenzae, but no exceptional activity against anaerobes.

Aerobiosis↗
PubMed1975

Cytoplasmic induction of changes in the ultrastructure of the Acetabularia nucleus and perinuclear cytoplasm.

The ultrasturcture of the cell nucleus and perinuclear cytoplasm in Acetabularia is quite different in young and old cells. When a nucleus of an old cell was implanted into the cytoplasm of a young cell the nucleus assumed the morphology typical of a young cell within less than 10 days. The cytoplasm of an old cell was able to induce the reverse change in an implanted nucleus from a young cell. This cytoplasmic induction of nuclear ageing appeared to proceed more rapidly than rejuvenation.

Acetabularia↗
PubMed1975

Vitamin A a absorption - nutritional aspects.

A brief review of the present knowledge of vitamin A (both performed and precursor forms) absorption is outlined with special emphasis on the dietary factors involved in this process. Some details are discussed related to the techniques used for measurement of vitamin A absorption from different sources and under different experimental conditions. Suggestions are also made to standardize appropriate procedure in this respect; this might enable comparisons and wide use of respective results obtained in various laboratories. Nutritional significance, including advantages or disadvantages of the liver test in these studies, is specifically highlighted with special reference to the determination of vitamin A bio-potency in various products. Some selected results and experience in this field are briefly presented.

Animals↗