Changes in muscle strength, muscle fibre size and myofibrillar gene expression after immobilization and retraining in humans

1. Changes in muscle strength, vastus lateralis fibre characteristics and myosin heavy-chain (MyoHC) gene expression were examined in 48 men and women following 3 weeks of knee immobilization and after 12 weeks of retraining with 1866 eccentric, concentric or mixed contractions. 2. Immobilization reduced eccentric, concentric and isometric strength by 47 %. After 2 weeks of spontaneous recovery there still was an average strength deficit of 11 %. With eccentric and mixed compared with concentric retraining the rate of strength recovery was faster and the eccentric and isometric strength gains greater. 3. Immobilization reduced type I, IIa and IIx muscle fibre areas by 13, 10 and 10 %, respectively and after 2 weeks of spontaneous recovery from immobilization these fibres were 5 % smaller than at baseline. Hypertrophy of type I, IIa and IIx fibres relative to baseline was 10, 16 and 16 % after eccentric and 11, 9 and 10 % after mixed training (all P < 0.05), exceeding the 4, 5 and 5 % gains after concentric training. Type IIa and IIx fibre enlargements were greatest after eccentric training. 4. Total RNA/wet muscle weight and ty I, IIa and IIx MyoHC mRNA levels did not change differently after immobilization and retraining. Immobilization downregulated the expression of type I MyoHC mRNA to 0.72-fold of baseline and exercise training upregulated it to 0.95 of baseline. No changes occurred in type IIa MyoHC mRNA. Immobilization and exercise training upregulated type IIx MyoHC mRNA 2.9-fold and 1.2-fold, respectively. For the immobilization segment, type I, IIa and IIx fibre area and type I, IIa and IIx MyoHC mRNA correlated (r = 0.66, r = 0.07 and r = -0.71, respectively). 5. The present data underscore the role muscle lengthening plays in human neuromuscular function and adaptation.

Effects of three types of free-stall surfaces on preferences and stall usage by dairy cows

One important criterion in choosing appropriate housing systems for dairy cattle is that the freestall provides a comfortable surface for the cow. This paper describes two experiments testing the effects of commonly used lying surfaces on stall preference and stall usage by Holstein cows. In both experiments, 12 cows were housed individually in separate pens. Each pen contained three free stalls with a different surface: deep-bedded sawdust, deep-bedded sand, and a geotextile mattress covered with 2 to 3 cm of sawdust. The animals were restricted to each surface in turn, in a random order for either 2 (Experiment 1) or 3 d (Experiment 2). Both before and after this restriction phase, the animals were allowed access to all three surfaces, and preference was determined, based on lying times. Of the 12 cows used in Experiment 1, 10 preferred sawdust before and nine after the restriction phase. During the restriction phase, average lying times and number of lying events during the restriction phase were significantly lower for the sand-bedded stalls (P < or = 0.05), and standing times were higher on mattresses (P < or = 0.05), compared with sawdust. Although these cows had some experience with all three surfaces during the experiment, they had been housed in sawdust-bedded stalls during their previous lactation. Cows used in Experiment 2 had spent their previous lactation in sand bedded stalls. In this experiment, about half the cows preferred sand and half sawdust, after the restriction phase. During the restriction phase of experiment, lying times and number of lying events were lower, and standing times were higher when the animals were restricted to the mattresses compared to either sand or sawdust (P < or = 0.05). These results indicate that (1) free stall surface can affect both stall preferences and stall usage, and (2) mattresses are less preferred.

Pathogenesis of hypocalcemia in primary hypomagnesemia: normal end-organ responsiveness to parathyroid hormone, impaired parathyroid gland function

Hypocalcemia is a frequent feature of hypomagnesemia in man and several other species. To elucidate the cause of this hypocalcemia, we have studied a child with primary hypomagnesemia and secondary hypocalcemia during magnesium supplementation when he was normomagnesemic and normocalcemic and after magnesium restriction for 16 days when he quickly became hypomagnesemic (0.5 meq/liter) and hypocalcemic (3.4 meq/liter) and had positive Chvostek's and Trousseau's signs. Whether in the normomagnesemic or hypomagnesemic state, intravenous bovine parathyroid extract (PTE) 8 U. S. P. U/kg promptly caused transient increases in the urinary phosphate excretion, renal phosphate clearance and cyclic AMP excretion. The magnitudes of these responses were similar in the two states, and similar to those observed in a hypoparathyroid patient. When the patient was hypomagnesemic and hypocalcemic, intramuscular PTE, 8 U/kg at 8-h intervals for four doses promptly caused hypercalcemia. The findings indicate that the end-organs were responsive to parathyroid hormone. The concentrations of serum parathyroid hormone (PTH) were normal in the normomagnesemic state ranging from 0.15 ng/ml to 0.40 ng/ml. Serum PTH did not increase in the hypomagnesemic state in spite of hypocalcemia. Indeed, PTH became unmeasurable in four consecutive samples at the end of the period of magnesium restriction. The concentrations of serum calcitonin remained unmeasurable (< 0.10 ng/ml) throughout the study, implying that excess calcitonin was not the cause of hypocalcemia in magnesium depletion. The findings in this study support our thesis that magnesium depletion causes impaired synthesis or secretion of parathyroid hormone. This impairment would account for the hypocalcemia observed in the hypomagnesemic state.

Action selection and refinement in subcortical loops through basal ganglia and cerebellum

Subcortical loops through the basal ganglia and the cerebellum form computationally powerful distributed processing modules (DPMs). This paper relates the computational features of a DPM's loop through the basal ganglia to experimental results for two kinds of natural action selection. First, functional imaging during a serial order recall task was used to study human brain activity during the selection of sequential actions from working memory. Second, microelectrode recordings from monkeys trained in a step-tracking task were used to study the natural selection of corrective submovements. Our DPM-based model assisted in the interpretation of puzzling data from both of these experiments. We come to posit that the many loops through the basal ganglia each regulate the embodiment of pattern formation in a given area of cerebral cortex. This operation serves to instantiate different kinds of action (or thought) mediated by different areas of cerebral cortex. We then use our findings to formulate a model of the aetiology of schizophrenia.

Acquisition, carriage, and transmission of pneumococci with decreased antibiotic susceptibility in young children attending a day care facility in southern Israel

The prevalence and transmission of antimicrobial drug-resistant pneumococci was studied in 48 children attending a day care facility in southern Israel. Nasopharyngeal cultures were obtained every 2 weeks for 10 months, and antibiotic susceptibility of isolates was determined by disk diffusion and E-test. Relatedness of isolates was investigated by capsular typing, ribotyping, and arbitrarily primed polymerase chain reaction. Pneumococci were recovered during 362 (63%) of 573 fortnights, and 219 (60%) of these isolates showed decreased susceptibility to at least one drug; 154 (43%) were intermediately susceptible to penicillin and 51 (14%) were multiresistant. Combining the different typing methods showed that a limited number of clones circulated in the facility. Clones exhibiting decreased antibiotic susceptibility (especially 23F, intermediately susceptible to penicillin and resistant to trimethoprim-sulfamethoxazole, and multiresistant 6B) were more frequently isolated and persisted longer than did fully susceptible clones. By multivariate analysis, carriage of organisms with decreased antibiotic susceptibility was associated with young age, female sex, winter season, and exposure to antimicrobial drugs during the previous month.

The etiology of enamel hypoplasia: a unifying concept

In a study of children with chronic disorders of calcium and phosphate homeostasis, enamel hypoplasia was found in hereditary vitamin D-dependency rickets and in hypoparathyroidism, conditions characterized by hypocalcemia, and was not found in X-linked hypophosphatemic rickets, a condition in which the plasma calcium concentration is normal. The occurrence of enamel hypoplasia bore no relation to the plasma phosphate concentration. Enamel hypoplasia has also been reported in other pediatric disorders in which hypocalcemia is a major sign (for example, vitamin D deficiency, prematurity, and neonatal tetany). The existence of enamel hypoplasia in a hypoparathyroid or rachitic patient, when correlated with the chronology of enamel mineralization, helps to establish the time of onset of hypocalcemia. The observations led us to the hypothesis that a low serum calcium concentration during enamel formation is a specific determinant of enamel hypoplasia. This hypothesis may be relevant to the etiology of linear enamel hypoplasia, an endemic lesion of primary teeth in children of many Third World countries that predisposes the teeth to dental caries. The hypothesis may therefore be relevant also in explaining the prevalence of caries in the primary teeth of children in many underdeveloped countries.

Effect of a conjugate pneumococcal vaccine on the occurrence of respiratory infections and antibiotic use in day-care center attendees

BACKGROUND

Incidence and severity of respiratory infections are increased in day-care center attendees. Streptococcus pneumoniae is an important contributor to these infections.

OBJECTIVE

To examine whether the use of a pneumococcal conjugate vaccine could reduce the occurrence of respiratory infections and the ensuing antibiotic drug use in the day care.

METHOD

In this double blind, randomized, controlled study performed in 8 day-care centers located in Beer-Sheva, Israel, 264 toddlers ages 12 to 35 months at enrollment were randomized to receive either a 9-valent conjugate pneumococcal vaccine (conjugated to CRM197) or a control vaccine [conjugate meningococcus C vaccine (conjugated to CRM197)] and were followed for an average of 22 months. The main outcome measures were respiratory morbidity and antibiotic use.

RESULTS

An overall reduction of 7% in child months with > or = 1 reported illness episodes was observed among vaccinees (P = 0.008), and 85% of all episodes were related to the respiratory tract. Reductions of 15, 16 and 17% were observed in upper respiratory infections, lower respiratory problems and otitis media, respectively. An overall reduction of 17% in antibiotic days was observed [10% for upper respiratory infections, 20% for otitis and 47% for lower respiratory problems (P < or = 0.005 for each entity)]. The reduction in episodes and antibiotic use was greater for those <36 months of age than for the older children.

CONCLUSION

The reduction of respiratory problems, including those not traditionally considered of pneumococcal origin and the ensuing lowered antibiotic use in day-care center attendees by pneumococcal conjugate vaccination suggest a broader benefit from the vaccine than preventing invasive disease only.

Treatment of hypoparathyroidism and pseudohypoparathyroidism with metabolites of vitamin D: evidence for impaired conversion of 25-hydroxyvitamin D to 1 alpha,25-dihydroxyvitamin D

In hypoparathyroidism and pseudohypoparathyroidism, pharmacologic doses of vitamin D correct hypocalcemia, but the mechanism is unknown. In two children with hypoparathyroidism and one with pseudohypoparathyroidism we tested the hypothesis that in these conditions there is a defect in synthesis of 1 alpha,25-dihydroxyvitamin D3, the principal active metabolite of vitamin D. In both conditions, minute doses of the metabolite (0.04 to 0.08 mug per kilogram of body weight per day) quickly corrected hypocalcemia and increased intestinal calcium absorption. On the other hand, the effective dose of 25-hydroxyvitamin D3 to maintain normocalcemia was 3 to 4 mug per kilogram per day in the two conditions. Thus, the dosage ratio of 25-hydroxyvitamin D3 to 1 alpha,25-dihydroxyvitamin D3 approximated 100:1. By contrast this ratio was approximately 3:1 in two infants with vitamin D deficiency, a condition in which optimal metabolism of vitamin D would be expected. These findings suggest an impaired conversion of 25-hydroxyvitamin D to 1 alpha,25-dihydroxyvitamin D in both hypoparathyroidism and pseudohypoparathyroidism.

Free-Stall Dimensions: Effects on Preference and Stall Usage

In 2 experiments, free-stall dimensions were examined to determine how they affected stall preference, usage, cleanliness, and milk production in Holstein dairy cattle. In experiment 1, stall width (112 or 132 cm) and stall length (229 and 274 cm from curb to wall) were compared in a 2 x 2 factorial arrangement of stall treatments using 15 individually housed, non-lactating animals. Cows showed no clear preference for stall size as measured by lying time. When animals had no choice between stalls, average lying time was higher in the wide stalls than in the narrow stalls (10.8 vs. 9.6+/-0.3 h/24 h). Both length and width affected time spent standing with only the front hooves in the stall; total stall area is best explained by the variation associated with this behavior. In experiment 2, 27 lactating dairy cattle were alternately housed with access to stalls of 106, 116, or 126 cm in width using a cross-over design with exposure to each treatment lasting 3 wk. Animals spent an additional 42 min/24 h lying in stalls measuring 126 cm in width compared with stalls with only 106 cm between partitions. Free-stall width influenced the time spent standing with the front 2 hooves in the stall; animals averaged 58 min/24 h in the widest stalls and 85 min/24 h in the narrowest stalls. The amount of time spent standing with all 4 hooves in the stall tended to be longer in wider stalls, and these stalls were also most likely to become soiled with feces. Stall width did not affect the number of lying events or milk production. In conclusion, animals spent more time lying down, and less time was spent standing with only the front hooves in larger stalls, but larger stalls were also more likely to become soiled.

Prevalence and genotypic characterisation of Giardia in dairy calves from Western Australia and Western Canada

In this study, the prevalence of Giardia duodenalis infections was determined in Western Canadian and Western Australian dairy calves. Faecal samples were collected from Holstein calves located on a commercial dairy near Lethbridge, Alta., Canada (N=28) and from calves located on two commercial dairies located near Perth, WA, Australia (N=36). Faecal samples were examined for the presence of Giardia cysts using sucrose gradient centrifugation, followed by immunofluoresence microscopy. DNA was then extracted from Giardia isolates obtained from positive samples. A PCR based method was employed to amplify and sequence a 292bp region of the 16S-rRNA gene. Genetic sequences obtained from Giardia isolates were compared to each other and to previously sequenced isolates. Following a single faecal sample, 58% of Western Australian calves and 57% of Western Canadian calves were positive for Giardia. Geometric mean cyst counts/g of faeces were 839 for Western Australian calves and 3475 for Western Canadian calves, but these values did not differ significantly. Genetic sequences were obtained from 10 calves from Western Canada, while six sequences were obtained from Western Australian calves. Of the Western Canadian isolates, eight aligned with the proposed 'Hoofed livestock' genotype. Of the five isolates obtained from Western Australian calves, four sequences were identical to the 'Hoofed livestock' genotype. Two isolates from the Western Canadian calves and one isolate from the Western Australian calves had the identical genetic sequence to the Genotype (Assemblage) A sequence, a common human genotype. The results of this study demonstrate, for the first time, that Giardia infections occur in Western Australian calves. Also, calves from different geographical locations appear to be primarily infected with a Giardia genotype unique to hoofed livestock. However, calves can shed Giardia cysts potentially infective for humans. Thus, Giardia infections should be considered important to Australian dairy producers, and infections in calves may pose a risk to public health regardless of geographical location.

Olfaction and the "data" memory system in rats

A set of studies was conducted to characterize the memory system involved in successive olfactory discrimination learning in rats. Two odors emanated from different arms of a radial maze; one of the arms contained a water reward. After training on four or five pairs of odors (20 trials per day), rats learned to discriminate the members of a new pair in 5-10 trials. Experiments in which either member of the pair was compared with a novel cue indicated that the rats learn both positive and negative odors, rather than simply ignoring the negative cue. The memories for the odors were apparently persistent, and no evidence for retroactive interference from subsequent training was obtained. Training on 30 pairs did not result in any slowing of subsequent learning, which suggest that the capacity of the memory system for odors is substantial. In a second group of experiments, we tested whether rats distinguish between odors by identifying unshared subcomponents or instead treat odors in a gestalt (i.e., unitary) fashion. Animals trained on three component odors with two in common did not recognize the elements that were unshared when these were presented by themselves. Even when one of the two shared components was combined with the differentiating component into a cue (i.e., two thirds of the original three-component odor), the new cue was treated as a novel odor. However, inclusion of a previously learned simple odor in a complex odor did affect the learning of that odor.(ABSTRACT TRUNCATED AT 250 WORDS)

Intensive surveillance for infections in a three-year study of nursing home patients

The authors report the results of a 3-year (August 1984-May 1987) prospective study of intensive surveillance for nursing home-associated infections in 666 patients in a 300-bed nursing home in San Diego, California. Ninety-three percent (666 of 714) of the eligible subjects enrolled; 75% were women. The mean age of the subjects was 81.6 years. Lengths of stay ranged from 1 day to 1,025 days, with a mean of 166 days; the cumulative length of stay for all subjects was 110,746 days (303 years). Operational definitions that were heavily dependent on evaluation of clinical signs and symptoms were used by nurse practitioners in weekly or biweekly assessments of all patients to identify infections. The overall incidence of nursing home-associated infection was 7.1 infections/1,000 patient-days. Many of the infections would not have been recognized by persons less skilled than nurse practitioners. Among the 788 nursing home-associated infections identified, 362 (47%) were in the respiratory tract (286 lower respiratory and 76 upper respiratory); 200 (25%) were associated with skin and subcutaneous and mucous membranes; 140 (18%) were symptomatic urinary tract infections; 13 (2%) were bacteremia; and 73 (9%) were other infections.

Studies on retrograde and anterograde amnesia of olfactory memory after denervation of the hippocampus by entorhinal cortex lesions

The effect of hippocampal denervation on olfactory memory in rats was tested after interrupting the lateral olfactory tract projections at the level of the entorhinal cortex. When lesioned animals were trained to learn new odors, they showed no evidence of retention 3 h after acquisition. These results confirm earlier data on rapid forgetting in rats after hippocampal deafferentation and are in parallel to the anterograde amnesia typically found in humans with hippocampal damage. On the other hand, preoperatively learned information was minimally impaired after hippocampal deafferentation even if it was acquired within less than 1 h before the lesion. This finding differs from reports on humans as well as monkeys with hippocampal damage where memories formed during a critical time span of months or even years before the lesion are found to be impaired. This may suggest that the consolidation process in humans and rodents has different time scales or that the roles of the human and the rat hippocampal structure in memory formation are somewhat different.

Normal forces and myofibrillar disruption after repeated eccentric exercise

To investigate the "rapid-adaptation" phenomenon, we examined force, neural, and morphological adaptations in 12 subjects who performed 100 eccentric contractions with the quadriceps muscle (bout 1) and repeated the same exercise after a 2-wk hiatus (bout 2). Two days after bout 1, quadriceps muscle strength and surface electromyographic (EMG) activity declined approximately 37 and 28%, respectively, in the control group (n = 6). At day 2 after bout 1, significant increases occurred in patellar tendon reflex amplitude (approximately 25%), muscle soreness (fivefold), and serum creatine kinase (220%), and 65 +/- 12% of the total number of pixels in the EMG indicated myofibrillar disruption. At day 7 after bout 1, all variables returned to normal. At day 2 after bout 2, no significant changes occurred in force, EMG, creatine kinase, or soreness, but reflex amplitude increased, and 23 +/- 4% of the total number of pixels in the EMG still indicated myofibrillar disruption. The results suggest that the rapid force recovery following eccentric exercise is mediated at least in part by neural factors and that this recovery may occur independently of cell disruption.

Posttraumatic stress disorder and short-term outcome in early methadone treatment

The aim of this study was to determine treatment adherence relative to frequency of violence and posttraumatic stress disorders (PTSD) among new methadone patients. Ninety-six opiate-abusing patients were evaluated for childhood physical and sexual abuse (CPSA), adulthood exposures to violence (ADVIOL), PTSD, and treatment adherence. Overall, 43% of the subjects dropped out of treatment within 3 months of intake. Occurrence of trauma or PTSD did not predict drop-out rates. A 2 (Gender) x 2 (PTSD) analysis of covariance (ANCOVA) with severity of other drug use on admission as a covariate, however, revealed a main effect for PTSD, F(4, 71) = 7. 69, p < or =.01, such that those patients with current PTSD revealed significantly more ongoing drug use at 3 months (M = 24.3, SD = 20. 9) than those without (M = 8.9, SD = 11.8). Examination of ongoing cocaine use using a 2 (Gender) x 2 (PTSD) ANCOVA also revealed a main effect for PTSD, F(4, 17) = 8.24, p < or = .005, such that those patients with current PTSD revealed significantly more ongoing cocaine use at 3 months postadmission (M = 51.6, SD = 37.6) than those without (M = 24.3, SD = 20.9). For both genders, CPSA and ADVIOL were associated with higher rates of PTSD, which in turn predicted poorer treatment adherence as measured by ongoing co-occurring drug abuse 3 months postadmission. Results underscore the need for routine assessment and targeted treatment of trauma in methadone patients.