Developmental characteristics of histamine methyltransferase and phenylethanolamine-N-methyl-transferase of rat brain

The specific activity of histamine methyltransferase of rat brain increases rapidly from the 16th until the 25th day of gestation (7 days after birth). The specific activity of phenylethanolamine-N-methyl-transferase shows a rapid increase during the 1st and the 2nd week after birth, the adult values being obtained by the end of the 2nd week.     

Greater rate of decline in maximal aerobic capacity with age in physically active vs. sedentary healthy women

Using a meta-analytic approach, we recently reported that the rate of decline in maximal oxygen uptake (VO2 max) with age in healthy women is greatest in the most physically active and smallest in the least active when expressed in milliliters per kilogram per minute per decade. We tested this hypothesis prospectively under well-controlled laboratory conditions by studying 156 healthy, nonobese women (age 20-75 yr): 84 endurance-trained runners (ET) and 72 sedentary subjects (S). ET were matched across the age range for age-adjusted 10-km running performance. Body mass was positively related with age in S but not in ET. Fat-free mass was not different with age in ET or S. Maximal respiratory exchange ratio and rating of perceived exertion were similar across age in ET and S, suggesting equivalent voluntary maximal efforts. There was a significant but modest decline in running mileage, frequency, and speed with advancing age in ET. VO2 max (ml . kg-1 . min-1) was inversely related to age (P < 0.001) in ET (r = -0.82) and S (r = -0.71) and was higher at any age in ET. Consistent with our meta-analysic findings, the absolute rate of decline in VO2 max was greater in ET (-5.7 ml . kg-1 . min-1 . decade-1) compared with S (-3.2 ml . kg-1 . min-1 . decade-1; P < 0. 01), but the relative (%) rate of decline was similar (-9.7 vs -9. 1%/decade; not significant). The greater absolute rate of decline in VO2 max in ET compared with S was not associated with a greater rate of decline in maximal heart rate (-5.6 vs. -6.2 beats . min-1 . decade-1), nor was it related to training factors. The present cross-sectional findings provide additional evidence that the absolute, but not the relative, rate of decline in maximal aerobic capacity with age may be greater in highly physically active women compared with their sedentary healthy peers. This difference does not appear to be related to age-associated changes in maximal heart rate, body composition, or training factors.     

The genes for butanol and acetone formation in Clostridium acetobutylicum ATCC 824 reside on a large plasmid whose loss leads to degeneration of the strain

Degeneration is the process whereby Clostridium acetobutylicum ATCC 824 loses the capacity to produce acetone and butanol after repeated vegetative transfers or in continuous culture. Two degenerate mutants (M5 and DG1) of C. acetobutylicum ATCC 824 do not contain the four genes (ctfA, ctfB, adc, and aad) for acetone and butanol formation. Strain ATCC 824 contains a 210-kb plasmid (pSOL1) which is absent in M5 and DG1. pSOL1 carries the four acetone and butanol formation genes. A restriction map of pSOL1 was constructed by using ApaI, SmaI, SstII, and NarI digestions. M5 and DG1 could be complemented for acetone and butanol formation by expressing the corresponding genes (ctfA, ctfB, and adc for acetone; aad for butanol) on the plasmid. Degeneration of this strain thus appears to be the result of pSOL1 loss.     

Declining sperm counts in the United States? A critical review

PURPOSE: Recent reports suggest declining sperm counts in the United States. These reports did not include all available data and did not account for geographic variations noted in prior studies. We examined all available data on U.S. sperm counts and evaluated whether geographic variations account for the decline suggested. MATERIALS AND METHODS: We reviewed all 29 U.S. studies from 1938 to 1996 reporting manually counted semen analyses of 9,612 fertile or presumably fertile men. We determined mean sperm concentrations by geographic location with weighted analysis of variance, and assessed any changes with time by linear regression analysis. RESULTS: Mean sperm concentrations from New York were significantly higher than from all other U.S. cities (98.6 versus 71.6 x 10(6) sperm per cc, respectively, p = 0.006). There has been no statistically significant change with time for mean sperm concentrations reported from New York (p = 0.49) or from U.S. cities other than New York (p = 0.62). Analysis without separating by location revealed a decline (p = 0.047). CONCLUSIONS: Sperm concentrations are highest in New York compared to other U.S. cities. When accounting for this geographic difference and examining all available data, there appears to be no significant change in sperm counts in the U.S. during the last 60 years. Further studies addressing the causes of geographic variations are needed.     

Responses to the sensory properties of fat of neurons in the primate orbitofrontal cortex

The primate orbitofrontal cortex is a site of convergence of information from primary taste, olfactory, and somatosensory cortical areas. We describe the responses of a population of single neurons in the orbitofrontal cortex that responds to fat in the mouth. The neurons respond, when fatty foods are being eaten, to pure fat such as glyceryl trioleate and also to substances with a similar texture but different chemical composition such as paraffin oil (hydrocarbon) and silicone oil [Si(CH3)2O)n]. This is evidence that the neurons respond to the oral texture of fat, sensed by the somatosensory system. Some of the population of neurons respond unimodally to the texture of fat. Other single neurons show convergence of taste inputs, and others of olfactory inputs, onto single neurons that respond to fat. For example, neurons were found that responded to the mouth feel of fat and the taste of monosodium glutamate (both found in milk), or to the mouth feel of fat and to odor. Feeding to satiety reduces the responses of these neurons to the fatty food eaten, but the neurons still respond to some other foods that have not been fed to satiety. Thus sensory-specific satiety for fat is represented in the responses of single neurons in the primate orbitofrontal cortex. Fat is an important constituent of food that affects its palatability and nutritional effects. The findings described provide evidence that the reward value (or pleasantness) of the mouth feel of fat is represented in the primate orbitofrontal cortex and that the representation is relevant to appetite.     

The coenzyme A-synthesizing protein complex and its proposed role in CoA biosynthesis in bakers'' yeast

An improved procedure is described for the recovery and purification of the coenzyme A-synthesizing protein complex (CoA-SPC) of Saccharomyces cerevisiae (bakers' yeast). The molecular mass of the CoA-SPC, determined prior to and following its purification, is estimated by Sephacryl S-300 size exclusion chromatography to be between 375,000-400,000. Two previously unreported catalytic activities attributed to CoA-SPC have been identified. One of these is CoA-hydrolase activity which catalyzes the hydrolysis of CoA to form 3',5'-ADP and 4'-phosphopantetheine, and the other is dephospho-CoA-pyrophosphorylase activity which catalyzes a reaction between 4'-phosphopantetheine and ATP to form dephospho-CoA. The dephospho-CoA then reacts with ATP, catalyzed by the dephospho-CoA-kinase, to reform CoA. This sequence of reactions, referred to as the CoA/4'-phosphopantetheine cycle, provides a mechanism by which the 4'-phosphopantetheine can be recycled to form CoA. Each turn of the cycle utilizes two mol of ATP and produces one mol of ADP, one mol of PPi, and one mol of 3',5'-ADP. Other than the hydrolysis of CoA by CoA-SPC, the 4'-phosphopantetheine for the cycle apparently could be supplied by alternate sources. One alternate source may be the conventional pathway of CoA biosynthesis. Intact CoA-SPC has been separated into two segments. One segment is designated apo-CoA-SPC and the other segment segment is referred to as the 10,000-15,000 M(r) subunit. The 5'-ADP-4'-pantothenic acid-synthetase, 5'-ADP-4'-pantothenylcysteine-synthetase, 5'-ADP-4'-pantothenylcysteine-decarboxylase, and CoA-hydrolase activities reside in the apo-CoA-SPC segment of CoA-SPC. Whereas the dephospho-CoA-kinase and the dephospho-CoA-pyrophosphorylase activities reside in the 10,000-15,000 M(r) subunit. Thus, the 10,000-15,000 M(r) subunit mimics the bifunctional enzyme complex that catalyzes the final two steps in the conventional pathway of CoA biosynthesis.