Biomedical subjects

R B Biggs

Publications and source records attributed to R B Biggs.

6 recordsLinked to original sources

PubMed1995

Detailed deletion mapping of chromosome 9p and p16 gene alterations in human borderline and invasive epithelial ovarian tumors.

We used PCR amplification of tandem repeats to study the pattern of allelic loss in borderline and invasive ovarian epithelial tumors using 12 primer pairs to generate a detailed deletion map of chromosome 9p. In the invasive ovarian carcinomas, there were three regions displaying high frequency of loss of heterozygosity (LOH) ranging from 31-38%. In contrast, LOH was a rare event among the borderline ovarian tumors, with one region revealing a rate of 20% and the remaining regions only 0-8% LOH. Therefore, allelic loss does not seem to be important for the development of borderline ovarian tumors. We also examined p16 gene expression and mutations in ovarian cancer cell lines and invasive and borderline ovarian tumor tissues. Southern blot analysis revealed no losses of the p16 gene in either the invasive or borderline ovarian tumors. However, the ovarian carcinoma cell lines showed a 50% homozygous deletion rate. SSCP analysis detected a mobility shift in only one (borderline) tumor. Since the primary invasive ovarian tumors did not show any deletions or mutations, it appears that p16 does not play a role in the pathogenesis of these tumors.

Carrier Proteins↗

PubMed1993

Insulin-like growth factor immunoreactivity increases in muscle after acute eccentric contractions.

The purpose of the study was to note whether insulin-like growth factor (IGF) immunoreactivity increased after eccentric contractions. IGF immunoreactivity in the rat tibialis anterior muscle was measured on 5 successive days (4-5 rats/group, n = 28) after an acute bout of 192 eccentric contractions elicited by electrical stimulation. The muscle tissue sections were immunocytochemically processed with rabbit anti-human IGF-I serum. Immunoreactivity was analyzed with videomicroscopy and computer-aided image processing. Four days after eccentric contractions, IGF immunoreactivity was significantly higher than control [0.081 +/- 0.073 (SD) absorbance at 480 nm vs. 0.026 +/- 0.018; P < 0.05]. The increases in IGF-I immunoreactivity were mostly within the muscle fibers. These results suggest that an acute bout of eccentric exercise increases IGF-I immunoreactivity in rat type II muscle 4 days postexercise.

Animals↗

PubMed1991

Cytochrome c mRNA levels decrease in senescent rat heart.

The concentration of mitochondria decreases in the heart as rodents age from maturity to senescence. The reason for this change is not known. One purpose of the present study was to determine if cytochrome c mRNA, representative of proteins of the inner mitochondrial membrane, decreased in the hearts of Fischer 344 rats as they aged from 12 to 24 months. Twenty-two percent less cytochrome c mRNA existed per given quantity of extracted RNA from the heart in 24-month-old rats as compared with the 12-month-old group. No change in the quantities of cardiac alpha-actin mRNA, Ca2+/calmodulin protein kinase II mRNA or 18S rRNA was noted between 12- and 24-month-old hearts. Thus, the decrease in cytochrome c mRNA suggests that decreases in mRNAs for proteins of the inner mitochondrial membrane could play some role in the diminished concentration of mitochondria that exists in the senescent heart.

Actins↗

PubMed1990

Protein synthesis rate is not suppressed in rat heart during senescence.

The purpose of these experiments was to determine whether mixed protein synthesis rates in hearts of Fischer 344 rats were decreased from maturity to senescence. When compared with 12-mo-old rat hearts, hearts from 23- to 25-mo-old rats had 13% lower concentrations of noncollagen protein, 9% less non-collagen protein per heart, 10% higher ratio of heart wet weight-to-body weight, and no difference in the basal rate of mixed protein synthesis, when expressed as fractional rate per day. Despite the 9% decrease in total noncollagen protein in 23- to 25-mo-old rat hearts, the derived value for milligrams protein synthesized per day was not different between age groups. When triiodothyronine was given for 3 days to mature and senescent rats, fractional rates of mixed protein synthesis were increased by similar percents (57-70%) in hearts from these two age groups. Basal and triiodothyronine-stimulated RNA concentrations in hearts of 12-mo-old and 23- to 25-mo-old rats were not different. These observations showed no decrease in either the basal or the maximal thyroid-stimulated rates of mixed protein synthesis in the hearts between mature and senescent rats. Thus an aging-programmed downregulation of mixed protein synthesis rates within cardiac muscle did not occur in the senescent Fischer 344 rat heart in this study.

Aging↗

PubMed1989

Daily running for 2 wk and mRNAs for cytochrome c and alpha-actin in rat skeletal muscle.

The purpose of the study was to determine whether daily running durations that were 7-14% of the durations employed in the chronic stimulation protocols (consisting of 24 h of daily indirect electrical stimulation of skeletal muscles) still resulted in increases in a mitochondrial protein mRNA. Adult female rats were run 100 min/day on motor-driven treadmills for 2 wk. Documentation that rats underwent the stated training program was obtained by a 30-41% increase in citrate synthase activity in hindlimb muscles after 2 wk of the training. Cytochrome c mRNA was increased 17-56% in hindlimb muscles after the 2-wk training program. Thus shorter durations of exercise (100 min/day rather than 24 h/day) can increase cytochrome c mRNA. alpha-Actin mRNA increased 61-62% in fast-twitch muscles in the hindlimbs of the same rats that underwent the 2 wk of run training but did not increase in the predominantly slow-twitch soleus muscle. The increase in alpha-actin mRNA was unexpected, since it is well known that this type of physical exercise does not increase the size of fast-twitch skeletal muscle.

Actins↗

PubMed1989

Protein metabolism and beta-myosin heavy-chain mRNA in unweighted soleus muscle.

To investigate the relative influence of protein synthetic and degradative control mechanisms in vivo during skeletal muscle atrophy, we measured myofibril and total mixed protein synthesis rates in muscles of rats prevented from hindlimb weight-bearing for 5 h and 7 days. Protein synthesis rates were determined by infusing the animals with [3H]Leu for 5 h and measuring the specific activity of [3H]Leu in the aminoacyl-tRNA precursor and protein product fractions of the muscles. In the soleus muscle, myofibril protein synthesis rates decreased from a control value of 5.9 to 4.6%/day during 5 h of hindlimb unweighting and to 2.4%/day after 7 days of hindlimb unweighting. The relatively more phasic muscles (plantaris, medial gastrocnemius, quadriceps) showed a tendency for increased myofibril protein synthesis rates (117-127% of control) during the first 5 h followed by a decrease (46-62% of control) at 7 days of hindlimb unweighting. A predicted time course of soleus muscle myofibril protein degradation rate was obtained from a numerical model of the decrease in soleus myofibril protein synthesis rate as a first-order process [half-time (t1/2) = 0.3 day by least-squares fit] and the time course of soleus muscle myofibril protein previously observed with hindlimb unweighting (Thomason et al., J. Appl. Physiol. 63: 130-137, 1987). The degradation rate model makes specific, testable predictions for the mechanism of myofibril protein degradation during soleus muscle atrophy: 1) the first-order degradation rate constant does not obtain a fixed value over a 24-day period but is continuously changing throughout atrophy, and 2) the first-order degradation rate constant changes on a time scale slower than protein synthesis rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗