Ontogeny of gastric acid secretion in the rat: evidence for multiple response systems.

Gastric acid secretion has been thought to depend on histamine stimulation of the parietal cell. However, in the 2-week-old rat neither exogenous histamine nor the H-2 receptor agonist impromidine stimulates acid secretion, whereas pentagastrin and the cholinergic agent bethanechol are potent stimuli. At this age, the effect of pentagastrin in acid secretion is not blocked by the H-2 receptor antagonist cimetidine, nor is it potentiated by impromidine. These data suggest that, in the rat pup, the acid secretory response to pentagastrin and cholinergic agents occurs before the histamine-mediated system is functional and operates independently of the actions of histamine.

Early maternal separation increases gastric ulcer risk in rats by producing a latent thermoregulatory disturbance.

Rat pups that are separated early from their mothers, at postnatal day 15, become hypothermic when subjected to physical restraint on postnatal day 30. Restraint of separated pups also elicits an unusually high incidence of gastric erosions, as well as insomnia and an increase in quiet wakefulness. If hypothermia during restraint is prevented, neither the erosions nor the behavioral responses occur. Rat pups separated at the customary age (postnatal day 22) do not become hypothermic during restraint, and the restraint of such pups is not associated with either gastric erosion or insomnia.

Vertical transmission of acquired ulcer susceptibility in the rat.

Premature separation of rat pups from their dams greatly increases their susceptibility to restraint-induced gastric erosions. When prematurely separated female rats grow to adulthood and mate with stock males, their normally reared F 1 progeny also have increased susceptibility to restraint-induced erosions. Cross-fostering studies show that prenatal rather than postnatal factors transmit this susceptibility to the F 1 progeny.

alpha-Methyldopa and depression: a clinical study and review of the literature.

A review of the literature showed that a high incidence or prevalence of depression in patients being treated with alpha-methyldopa has never been documented. In their study of hypertensive patients in a general medical clinic the authors found that symptoms of depression were no more common in 42 patients treated with alpha-methyldopa than in 38 patients treated with other antihypertensive agents. As with other centrally active agents, alpha-methyldopa appears able to produce many different behavioral symptoms, including mood changes, in predisposed individuals. Because alpha-methyldopa is a DOPA decarboxylase inhibitor but does not consistently affect mood or induce depression, its effects do not support a catecholamine hypothesis of depression.

The Drosophila gene 2A5 complements the defect in mitochondrial F1-ATPase assembly in yeast lacking the molecular chaperone Atp11p.

Assembly of mitochondrial F1-ATPase in Saccharomyces cerevisiae requires the molecular chaperone, Atp11p. Database searches have identified protein sequences from Schizosaccharomyces pombe and two species of Drosophila that are homologous to S. cerevisiae Atp11p. A cDNA encoding the putative Atp11p from Drosophila yakuba was shown to complement the respiratory deficient phenotype of yeast harboring an atp11::HIS3 disruption allele. Furthermore, the product of this Drosophila gene was shown to interact with the S. cerevisiae F1 beta subunit in the yeast two-hybrid assay. These results indicate that Atp11p function is conserved in higher eukaryotes.

ATP13, a nuclear gene of Saccharomyces cerevisiae essential for the expression of subunit 9 of the mitochondrial ATPase.

The respiratory deficient nuclear mutant of Saccharomyces cerevisiae, N9-168, assigned to complementation group G95 was previously shown to lack subunit 9, one of the three mitochondrially encoded subunits of the Fo component of the mitochondrial ATPase. As a consequence of the structural defect in Fo, the ATPase activity of G95 mutants is not inhibited by rutamycin. The absence of subunit 9 in N9-168 has been correlated with a lower steady-state level of its mRNA and an increase in higher molecular weight precursor transcripts. These results suggest that the mutation is most likely to affect either translation of the oli1 mRNA or processing of the primary transcript. We have isolated a nuclear gene, designated ATP13, which complements the respiratory defect and restores rutamycin-sensitive ATPase in G95 mutants. Disruption of ATP13 induces a respiratory deficiency which is not complemented by G95 mutants. The nucleotide sequence of ATP13 indicates a primary translation product with an Mapp of 42,897. The protein has a basic amino terminal signal sequence that is cleaved upon import into mitochondria. No significant primary structure homology is detected with any protein in the most recent libraries.

Genetically obese (ob/ob) mice are predisposed to gastric stress ulcers.

Genetically obese (ob/ob) mice and lean littermate controls were food deprived and subsequently physically restrained at normal room temperatures. Obese mice became hypothermic and developed gastric stress ulcers. Lean mice maintained normal body temperatures and did not form gastric ulcers. Oxygen consumption was measured during food deprivation and restraint. Obese and lean mice had parallel metabolic responses, with obese animals using significantly less oxygen at all times. The predisposition to formation of gastric ulcers is a new phenotypic expression of the ob/ob genotype. The pathogenesis of this susceptibility appears to be related to a genetic disturbance in heat production.

Early life events and peptic ulcer susceptibility: an experimental model.

In the rat premature separation from the mother increases the probability that gastric erosions will occur when the animal is subjected to physical restraint later in life. This increased susceptibility to erosion formation is induced by the early loss of maternal milk and is expressed as a disturbance of body temperature regulation at the time of restraint. One of the gastric consequences of the thermoregulatory disturbance appears to be an increase in acid secretion during restraint. The increased susceptibility to restraint-induced erosion formation in prematurely separated rats may reflect a disruption of the normal developmental organization of functionally related systems.

Plasma tryptophan to large neutral amino acid ratios in depressed and normal subjects.

The ratios of total and free plasma tryptophan to the sum of five large neutral amino acids (LNAAs) were found to be significantly lower in a group of 16 depressed inpatients compared to nine normal subjects after oral loading with L-tryptophan. The group differences in these ratios were significant before, and 2 weeks after starting treatment with a tricyclic antidepressant. Plasma tryptophan ratios and severity of depression were not significantly correlated.

Reduced fat stores after early weaning: a correlate of vulnerability of stress ulcers.

Rats prematurely weaned at day 15 (15w) are more susceptible to restraint-induced gastric erosions (RGEs) than rats weaned normally at day 21 (21w). Increased RGE susceptibility is linked to nutritional changes occurring during premature weaning and to a disturbance of temperature regulation during restraint. Here we examine the hypotheses that: premature weaning leads to decreases in fat stores, a decrease in fat stores is associated with the occurrence of RGEs and hypothermia. Wet weights of white and brown adipose tissue deposits were determined in 30 day old 15w and 21w rats before or subsequent to food deprivation and restraint. In additional 21w animals we excised bilateral inguinal fat depots or interscapular brown adipose tissue (BAT) prior to food deprivation and restraint. Stomachs were examined for the presence of RGEs. Early weaned (15w), but not 21w rats became hypothermic and developed RGEs. White and brown adipose tissue weighed significantly less in 15w rats than in 21w rats, and 15w rats used a larger percentage of white adipose tissue. Excision of BAT, but not white adipose tissue increased RGE susceptibility of 21w rats. We conclude that the occurrence of RGEs in 15w rats is associated with decreased fat stores. Furthermore, the results suggest that BAT protects against RGE formation.

Some effects of a split litter cross foster design applied to 15 day old rat pups.

Rat litters were divided and cross fostered on a postnatal Day 15 so that each mother had 4 of her own pups and 4 pups of a second litter, until weaning at 21 days. Daily weight and body temperature measurements made between Day 15 and 21 showed no differences between foster pups and pups who stayed with their biological mothers. However, by the age of 30 days, foster pups weighed less than pups reared by their own (biological) mothers; and foster pups at that age did not survive food deprivation as well as the pups reared by their biological mothers. In their Day 30 weights and the capacity to survive food deprivation, foster pups resembled pups that had been permanently separated from their mothers on postnatal Day 15. We conclude that the split cross foster design may introduce variability rather than reduce it. Nonetheless, this design may be useful in the experimental investigation of maternal behavior and mother-pup interactions in the rat.

Postprandial sleep and thermogenesis in normal men.

Twelve normal male subjects were given low- (16.77 kj/kg) and high- (54.49 kj/kg) calorie liquid carbohydrate lunch meals on 4 days, during which measures of sleep EEG, thermogenesis (heat production), core body temperature, and skin surface temperature were obtained. On 2 days subjects were required to remain awake, and on 2 days sleep was allowed. Both meals were administered in each condition. On the days that subjects were instructed to remain awake, thermogenesis was significantly greater following high-calorie meals than low-calorie meals, and both meal conditions produced levels of thermogenesis that were greater than those observed when sleep was allowed. When given the opportunity, 11 of 12 subjects slept following both low- and high-calorie meals. There was no difference between meal conditions in the total minutes or percent of stages 1, 2, 3/4, or rapid eye movement (REM) sleep following meals. However, the onset of postprandial sleep episodes was associated with the peak of the postprandial rise in thermogenesis, and the occurrence of sleep was followed by precipitous and statistically significant declines in thermogenesis and core body temperature, as well as increases in skin surface temperature. These data suggest that postprandial sleep is associated with rises in thermogenesis, and that its occurrence decreases postprandial heat production and body temperature.

Chronobiologic factors in experimental stress ulcer.

The available literature on chronobiologic factors in experimental stress ulcer is extremely small and thematically limited. It focuses almost exclusively on circadian rhythms and, within that, on rhythms related to light-dark cycles, activity and body temperature. Among these, only differences in ulcer induction related to circadian activity patterns have been adequately demonstrated. Other circadian patterns and other temporal phase relationships might be profitably explored, including those related to postnatal development. It is also likely that the important relationships between biorhythms and stress ulcer are not limited to ulcer induction. Future studies should address chronobiologic factors in predisposition, severity of illness, the probability of recovery and response to various therapeutic interventions.

The developmental physiology of the stomach: possible contributions to the regulatory disturbances of duodenal ulcer disease.

Several different disturbances in the regulation of acid secretion have been found in persons with duodenal ulcer disease (DU). This paper examines the possibility that some of these regulatory disturbances might arise during postnatal development. The regulation of acid secretion is not fixed in adult form at birth, in either animals or humans. Instead, these regulatory processes continue to change during postnatal development. Examples are developmental changes in the responsiveness of the stomach to parietal cell stimulants and developmental increases and decreases in basal and maximal acid output. The unfolding of these developmental changes requires complex regulatory adjustments. It is possible that untoward environmental circumstances could induce "errors" in these regulated changes or adjustments. Some errors might persist as disturbances in the regulation of acid secretion seen in patients with DU.

Bacterial production and characterization of ATP11, a yeast protein required for mitochondrial F1-ATPase assembly.

ATP11 is a nuclear gene product that is required for assembly of mitochondrial F1-ATPase in the yeast Saccharomyces cerevisiae. ATP11 is synthesized in the yeast cytoplasm with an N-terminal targeting sequence. Following import into mitochondria, the leader sequence is cleaved, generating the functional form of the protein. ATP11 is present in small amounts in yeast mitochondria, which has made it difficult to study its role in F1 assembly. We have developed a bacterial expression system for the overproduction of the mature form of ATP11 and its biotinated derivative, BTATP11. Yeast complementation assays showed that the DNA fragments used to produce ATP11 and BTATP11 in bacteria encode biologically active proteins. The recombinant proteins produced in bacteria were purified to homogeneity and their physical characteristics were shown to be similar to those of the mitochondrial ATP11 protein synthesized in yeast.

Characterization of mutations in the beta subunit of the mitochondrial F1-ATPase that produce defects in enzyme catalysis and assembly.

The ATP2 gene, coding for the beta subunit of the mitochondrial F1-ATPase, was cloned from nine independent isolates of chemically mutagenized yeast. Seven different mutant alleles were identified. In one case the mutation occurs in the mitochondrial targeting sequence (M1I). The remaining six mutations map to the mature part of the beta subunit protein and alter amino acids that are conserved in the bovine heart mitochondrial and Escherichia coli beta subunit proteins. Biochemical analysis of the yeast atp2 mutants identified two different phenotypes. The G133D, P179L, and G227D mutations correlate with an assembly-defective phenotype that is characterized by the accumulation of the F1 alpha and beta subunits in large protein aggregates. Strains harboring the A192V, E222K, or R293K mutations assemble an F1 of normal size that is none-the-less catalytically inactive. The effect of the atp2 mutations was also analyzed in diploids formed by crossing the mutants to wild type yeast. Hybrid enzymes formed with beta subunits containing either the G133D, E222K, or R293K mutations are compromised for steady-state ATPase activity. The display of partial dominance confirms the importance of Gly133 for structural stability and of Glu222 and Arg293 for catalytic cooperativity.

Identification of functional domains in Atp11p. Protein required for assembly of the mitochondrial F1-ATPase in yeast.

The Atp11p protein of Saccharomyces cerevisiae is required for proper assembly of the F1 component of the mitochondrial ATP synthase. The mutant atp11 genes were cloned and sequenced from 12 yeast strains, which are respiratory-deficient due to a defect in Atp11p function. Four of the mutations mapped to the mitochondrial targeting domain (amino-terminal 39 amino acids) of Atp11p. All the genetic lesions found in the mature protein sequence were shown to be nonsense mutations. This result is consistent with the idea that Atp11p activity is provided, principally, by the overall structure of a functional domain, and not by specific amino acid residues in a localized active site. Amino-terminal (Edman) sequence analysis of fragments derived from limited proteolysis of purified Atp11p, and in vivo functional characterization of deletion mutants, were employed to locate the position of the active region in the protein. Three domains, separated by proline-rich sequences, were identified in the mature protein. The active domain of Atp11p was mapped to the sequence between Phe-120 and Asn-174. The domains proximal (Glu-40 through Ser-109) and distal (Arg-183 through Asn-318) to the active region were found to be important for the protein stability inside mitochondria.