Influence of aging on the in vivo properties of human patellar tendon.

Tendons are important for optimal muscle force transfer to bone and play a key role in functional ability. Changes in tendon properties with aging could contribute to declines in physical function commonly associated with aging. We investigated the in vivo mechanical properties of the patellar tendon in 37 men and women [11 young (27 +/- 1 yr) and 26 old (65 +/- 1 yr)] using ultrasonography and magnetic resonance imaging (MRI). Patella displacement relative to the tibia was monitored with ultrasonography during ramped isometric contractions of the knee extensors, and MRI was used to determine tendon cross-sectional area (CSA) and signal intensity. At peak force, patellar tendon deformation, stress, and strain were 13 (P = 0.05), 19, and 12% less in old compared with young (P < 0.05). Additionally, deformation, stiffness, stress, CSA, and length were 18, 35, 41, 28, and 11% greater (P < 0.05), respectively, in men compared with women. After normalization of mechanical properties to a common force, no age differences were apparent; however, stress and strain were 26 and 22% higher, respectively, in women compared with men (P < 0.05). CSA and signal intensity decreased 12 and 24%, respectively, with aging (P < 0.05) in the midregion of the tendon. These data suggest that differences in patellar tendon in vivo mechanical properties with aging are more related to force output rather than an age effect. In contrast, the decrease in signal intensity indirectly suggests that the internal milieu of the tendon is altered with aging; however, the physiological and functional consequence of this finding requires further study.

Successful treatment of acute humoral rejection in a heart transplant patient.

Eight months after undergoing orthotopic heart transplantation, a patient had hypotension and biventricular heart failure. Endomyocardial biopsy specimens showed a modest cellular infiltrate, predominantly of plasma cells, and progressive myocyte injury, suggesting a humoral rejection process. The patient was treated with Minnesota antilymphoblast globulin and aggressively with plasmapheresis, resulting in evidence of myocyte repair, improved hemodynamics, and long-term survival.

Assay of rifampicin in serum.

Two methods for the assay of rifampicin in serum are described. The first is a conventional plate diffusion method, measuring concentrations down to 0.02 mug/ml, and the second a chemical extraction followed by measurement of the inhibition of uptake of (14)C-uridine by Staphylococcus aureus, which estimates in the range of 0.02 to 0.001 mug/ml. The methods were used to measure serum concentrations in man following doses of about 1050 mg and 75 mg rifampicin.

Bioavailability of Chinese rifapentine during a clinical trial in Hong Kong.

SETTING: A clinical trial of rifapentine in Hong Kong. OBJECTIVE: Assessment of the bioavailability of the Chinese rifapentine used in the trial. DESIGN: The content of rifapentine in serum samples taken from 287 patients during the administration of four batches of the drug was measured by microbiological assay. RESULTS: An initial comparison of areas under curve obtained in a random allocation to 40 patients of rifapentine either of Western or Chinese origin indicated that the bioavailability of the Chinese drug was 74% of the Western drug. The bioavailability of the second batch was found to be about 66% of the Western drug. The dose of the last two batches of rifapentine was therefore increased from the planned 600 mg to 750 mg, or briefly to 900 mg; serum concentrations were then similar to those obtained with the Western drug. Bioavailability did not change during the use of each drug batch. CONCLUSION: A comparison of the results obtained in the trial with the initial two batches and the final batches will estimate the effects of rifapentine dose size on its efficacy and toxicity.

Comparison of Chinese and Western rifapentines and improvement of bioavailability by prior taking of various meals.

Bioavailability was measured by rifapentine (RPE) serum concentrations and by the urinary ratio between RPE and creatinine, in specimens obtained 4-50 h after 600 mg RPE preceded by food. The bioavailabilities of RPEs manufactured in China and by a Western manufacturer were similar after a standard English breakfast, and serum concentrations were also similar to those obtained in an earlier Italian study following a complex meal. Although absorption of RPE was unsatisfactory after lipid-rich biscuits or shortbread, absorption after egges and toast was excellent and was nearly as good after a fast-food sandwich. The urinary measure of bioavailability at 26 h appeared as efficient as peak serum estimations at 6, 8 and 26 h. Fast-food sandwiches are being taken before RPE in a current clinical trial of Chinese RPE in Hong Kong.

In vitro metabolism of formononetin and biochanin A in bovine rumen fluid.

The phyto-estrogens formononetin (7-hydroxy-4'methoxyisoflavone) and biochanin A (5-7-dihydroxy-4'-methoxyisoflavone) were independently incubated in vitro at 39 degrees C in bovine rumen fluid from a fistulated steer receiving an alfalfa hay diet. Formononetin was incubated in studies 1 and 2, whereas biochanin A was incubated in study 3. The isoflavones were separated and quantified by high performance liquid chromatography. In study 1, formononetin concentration, 14.80 micrograms/ml at time 0, declined to 1.16 micrograms/ml by 12 h and to .76 micrograms/ml by 24 h. Daidzein (7,4-dihydroxyisoflavone), .18 micrograms/ml at time 0, peaked at 12.92 micrograms/ml at 6 h and decreased to 1.30 micrograms/ml by 24 h. Equol (7,4'-dihydroxyisoflavan), detected at 6 h, peaked at 16.94 micrograms/ml at 18 h and dropped to 12.64 micrograms/ml at 24 h. In incubation study 2, formononetin declined from 17.57 micrograms/ml at time 0 to 7.08 micrograms/ml by 6 h. Daidzein concentration was 1.75 micrograms/ml at time 0 and increased to 12.03 micrograms/ml by 6 h. Equol was detected at 3 h and increased to 2.32 micrograms/ml at 6 h. The half-lives were 4.3 for formononetin and 9.8 h for daidzein in this in vitro system. In study 3, biochanin A, 8.54 micrograms/ml at time 0, decreased to 0 micrograms/ml by 12 h in incubation 3, whereas genistein (5,7,4'-trihydroxyisoflavone), 3.17 micrograms/ml at 1 h, peaked at 7.35 micrograms/ml at 4 h and decreased to .32 micrograms/ml at 24 h. Equol was not detected in incubation study 3. The half-lives of biochanin A and genistein were 3.9 and 5.5 h, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced transfer of male accessory gland proteins and monandry in female Aedes aegypti mosquitoes.

We examined whether female Aedes aegypti (L.) mosquitoes would remate after they first mated with a male that was reared on a suboptimal larval diet and that as a result, transferred reduced amounts of male accessory gland proteins. Accessory gland proteins from males labeled with 3H leucine were not detected in females allowed to male mate with the labeled males after they first mated with either low diet or high diet males. The amount of the male accessory gland protein transferred by smaller, low diet males was adequate to terminate female receptivity, even after one gonotrophic cycle, and females of this species appear to be monogamous.

Soy-dairy protein blend and whey protein ingestion after resistance exercise increases amino acid transport and transporter expression in human skeletal muscle.

Increasing amino acid availability (via infusion or ingestion) at rest or postexercise enhances amino acid transport into human skeletal muscle. It is unknown whether alterations in amino acid availability, from ingesting different dietary proteins, can enhance amino acid transport rates and amino acid transporter (AAT) mRNA expression. We hypothesized that the prolonged hyperaminoacidemia from ingesting a blend of proteins with different digestion rates postexercise would enhance amino acid transport into muscle and AAT expression compared with the ingestion of a rapidly digested protein. In a double-blind, randomized clinical trial, we studied 16 young adults at rest and after acute resistance exercise coupled with postexercise (1 h) ingestion of either a (soy-dairy) protein blend or whey protein. Phenylalanine net balance and transport rate into skeletal muscle were measured using stable isotopic methods in combination with femoral arteriovenous blood sampling and muscle biopsies obtained at rest and 3 and 5 h postexercise. Phenylalanine transport into muscle and mRNA expression of select AATs [system L amino acid transporter 1/solute-linked carrier (SLC) 7A5, CD98/SLC3A2, system A amino acid transporter 2/SLC38A2, proton-assisted amino acid transporter 1/SLC36A1, cationic amino acid transporter 1/SLC7A1] increased to a similar extent in both groups (P < 0.05). However, the ingestion of the protein blend resulted in a prolonged and positive net phenylalanine balance during postexercise recovery compared with whey protein (P < 0.05). Postexercise myofibrillar protein synthesis increased similarly between groups. We conclude that, while both protein sources enhanced postexercise AAT expression, transport into muscle, and myofibrillar protein synthesis, postexercise ingestion of a protein blend results in a slightly prolonged net amino acid balance across the leg compared with whey protein.

Influence of acetaminophen and ibuprofen on in vivo patellar tendon adaptations to knee extensor resistance exercise in older adults.

Millions of older individuals consume acetaminophen or ibuprofen daily and these same individuals are encouraged to participate in resistance training. Several in vitro studies suggest that cyclooxygenase-inhibiting drugs can alter tendon metabolism and may influence adaptations to resistance training. Thirty-six individuals were randomly assigned to a placebo (67 ± 2 yr old), acetaminophen (64 ± 1 yr old; 4,000 mg/day), or ibuprofen (64 ± 1 yr old; 1,200 mg/day) group in a double-blind manner and completed 12 wk of knee extensor resistance training. Before and after training in vivo patellar tendon properties were assessed with MRI [cross-sectional area (CSA) and signal intensity] and ultrasonography of patellar tendon deformation coupled with force measurements to obtain stiffness, modulus, stress, and strain. Mean patellar tendon CSA was unchanged (P > 0.05) with training in the placebo group, and this response was not influenced with ibuprofen consumption. Mean tendon CSA increased with training in the acetaminophen group (3%, P < 0.05), primarily due to increases in the mid (7%, P < 0.05) and distal (8%, P < 0.05) tendon regions. Correspondingly, tendon signal intensity increased with training in the acetaminophen group at the mid (13%, P < 0.05) and distal (15%, P = 0.07) regions. When normalized to pretraining force levels, patellar tendon deformation and strain decreased 11% (P < 0.05) and stiffness, modulus, and stress were unchanged (P > 0.05) with training in the placebo group. These responses were generally uninfluenced by ibuprofen consumption. In the acetaminophen group, tendon deformation and strain increased 20% (P < 0.05) and stiffness (-17%, P < 0.05) and modulus (-20%, P < 0.05) decreased with training. These data suggest that 3 mo of knee extensor resistance training in older adults induces modest changes in the mechanical properties of the patellar tendon. Over-the-counter doses of acetaminophen, but not ibuprofen, have a strong influence on tendon mechanical and material property adaptations to resistance training. These findings add to a growing body of evidence that acetaminophen has profound effects on peripheral tissues in humans.

A new method to study in vivo protein synthesis in slow- and fast-twitch muscle fibers and initial measurements in humans.

The aim of this study was to develop an approach to directly assess protein fractional synthesis rate (FSR) in isolated human muscle fibers in a fiber type-specific fashion. Individual muscle fibers were isolated from biopsies of the vastus lateralis (VL) and soleus (SOL) obtained from eight young men during a primed, continuous infusion of [5,5,5-(2)H3]leucine performed under basal conditions. To determine mixed protein FSR, a portion of each fiber was used to identify fiber type, fibers of the same type were pooled, and the [5,5,5-(2)H3]leucine enrichment was determined via GC-MS. Processing isolated slow-twitch [myosin heavy chain (MHC) I] and fast-twitch (MHC IIa) fibers for mixed protein bound [5,5,5-(2)H3]leucine enrichment yielded mass ion chromatographic peaks that were similar in shape, abundance, and measurement reliability as tissue homogenates. In the VL, MHC I fibers exhibited a 33% faster (P<0.05) mixed protein FSR compared with MHC IIa fibers (0.068+/-0.006 vs. 0.051+/-0.003%/h). MHC I fibers from the SOL (0.060+/-0.005%/h) and MHC I fibers from the VL displayed similar (P>0.05) mixed protein FSR. Feasibility of processing isolated human muscle fibers for analysis of myofibrillar protein [5,5,5-(2)H3]leucine enrichment was also confirmed in non-fiber-typed pooled fibers from the VL. These methods can be applied to the study of fiber type-specific responses in human skeletal muscle. The need for this level of investigation is underscored by the different contributions of each fiber type to whole muscle function and the numerous distinct adaptive functional and metabolic changes in MHC I and MHC II fibers originating from the same muscle.

In vitro activities against mycobacteria of two long-acting rifamycins, FCE22807 and CGP40/469A (SPA-S-565).

The in vitro activities of two new long-acting rifamycins, FCE22807 a derivative of FCE22250, and CGP40/469A (SPA-S-565) were studied. When compared with rifampicin, the minimal inhibitory concentrations (MIC) against Mycobacterium tuberculosis of both were 4 times lower but neither was particularly active against rifampicin-resistant strains of M. tuberculosis nor against M. avium-intracellulare-scrofulaceum complex strains. A drug is likely to be particularly effective in widely spaced intermittent dosage if it has a long half-life and high bactericidal activity. When tested against M. tuberculosis in the logarithmic and in the stationary phase of growth, FCE22807 was amongst the most bactericidal of the rifamycins while CGP40/469A had little bactericidal activity.

Activity of the combination of fludalanine and cycloserine against mycobacteria in vitro.

The initial steps in the incorporation of alanine into the bacterial cell wall include the conversion of natural to D-alanine by a racemase followed by the coupling of 2 D-alanine molecules by a synthetase to yield a dipeptide. A combination of fludalanine (3-fluoro-2-deutero-D-alanine), an analogue of D-alanine that irreversibly inactivates the racemase, and cycloserine, which inhibits the synthetase, has been found to be more active against a wide range of non-mycobacterial organisms than either fludalanine or cycloserine alone. When tested against 16 strains of slowly growing mycobacteria including M. tuberculosis, the combination was no more active than cycloserine alone. However the cycloserine minimal inhibitory concentration (MIC) of the combination against the rapidly growing species M. phlei and M. fortuitum was much lower than the MIC of cycloserine alone, particularly with low ratios of fludalanine to cycloserine, and was within the range attainable by therapeutic cycloserine plasma concentrations in man, suggesting its possible use in the treatment of disease due to M. fortuitum.

In vitro activity of new rifamycins against rifampicin-resistant M. tuberculosis and MAIS-complex mycobacteria.

Comparisons were made of the in vitro activity of rifampicin, and the rifamycin derivatives, rifapentine, rifabutin, CGP 29861, CGP 7040 and CGP 27557, against rifampicin-sensitive and rifampicin-resistant strains of Mycobacterium tuberculosis and against the Mycobacterium avium/intracellulare/scrofulaceum (MAIS) complex. The new rifamycins had MICs four to eight times lower than those of rifampicin against sensitive M. tuberculosis strains. Of the 35 rifampicin-resistant strains of M. tuberculosis, 31% were sensitive to rifabutin but only 3-11% to the other rifamycins. The proportions of the MAIS strains found to be sensitive were 35% for rifampicin, 50-60% for CGP 27557, rifapentine and rifabutin and 85-92% for CGP 29861 and CGP 7040.

In vitro observations on the suitability of new rifamycins for the intermittent chemotherapy of tuberculosis.

The bactericidal activity of six new rifamycin derivatives--rifabutin (RBU), FCE 22250 (F22), rifapentine (RPE), CGP 29861 (C29), CGP 7040 (C70) and CGP 27557 (C27) and rifampicin (RMP)--have been measured against log phase and, as a better test of sterilising activity, against stationary phase cultures of Mycobacterium tuberculosis, H37Rv. The order of activity of 1.0 and 0.2 mg/l rifamycin against log phase cultures was RMP greater than RPE & C27 greater than RBU & C29 greater than C70. The order of activity of 1.0 and 0.4 mg/l, adjusted for stability of the rifamycin, against stationary phase cultures was F22 & RMP greater than RBU greater than RPE greater than C27 & C29 greater than C70. Viable counts were done during and after pulsed exposures of 6, 24 or 96 h to C29 and RMP. The curves were similar though C29 was less bactericidal and the lag period before recovery was 1-2 days longer. F22, having high bactericidal activity against stationary organisms and a long half-life, was considered likely to be the most effective sterilising drug.

In vitro properties of rifapentine (MDL473) relevant to its use in intermittent chemotherapy of tuberculosis.

In a comparison of in vitro properties of rifapentine (RIF) and rifampicin (RMP), the minimal inhibitory concentration of RIF against Mycobacterium tuberculosis in Tween-albumin liquid medium was usually 0.02 micrograms/ml, 2-3 times lower than for RMP; the bactericidal activity against a log phase culture was slightly less than that of RMP and the recovery after pulsed exposures to 1 microgram/ml of RIF or RMP lasting 6, 24 and 96 h was identical for the two rifamycins. These findings are used to interpret published data from the chronic experimental murine tuberculosis model and support the view that in the mouse, the efficacy of RIF in widely spaced intermittent chemotherapy is the result of its long half-life.

Efficacy of intermittent pyrazinamide in experimental murine tuberculosis.

CFLP mice were infected intravenously with Mycobacterium tuberculosis strain H37Rv and the progress of chemotherapy was followed by counts of viable bacilli in the lung and spleen. After spleen counts had reached log10 7.0, 12 experimental groups, each containing 10 mice, were treated for 8 weeks with pyrazinamide (PZA) given in mean daily dosages of 100, 200 or 400 mg/kg/day, with the interval between the doses within each dosage group being 1, 2, 4 or 8 days. All mice were also given 25 mg isoniazid/kg daily. An increase in the mean daily dosage from 100 mg PZA/kg to 400 mg PZA/kg resulted in a decrease of spleen viable counts at the end of treatment from log10 4.2 to log10 3.8. The organ counts, averaged over the full dosage range, were little altered by spacing out the interval between doses from 1-4 days, while increasing dose size proportionately: the counts with low mean dosages tended, however, to decrease (indicating improved efficacy) while those with high mean dosages increased (P less than 0.001). Counts increased when the interval was 8 days. Spacing out the doses while keeping the dose size constant resulted in progressive loss of efficacy. These findings suggest that, if PZA is given intermittently, the size of the dose should be increased, though not quite proportionately, to maintain full efficacy. Even with such an increase in dose, however, once weekly treatment would be less effective.

Bactericidal activity in vitro and in the guinea-pig of isoniazid, rifampicin and ethambutol.

Serial viable counts on Mycobacterium tuberculosis exposed in vitro to isoniazid, rifampicin and ethambutol in Tween-albumin liquid medium showed no bactericidal synergism between isoniazid and rifampicin and no influence of ethambutol on the bactericidal activity of isoniazid or isoniazid plus rifampicin. Guinea-pigs with moderately advanced experimental tuberculosis were treated fro 11 weeks with either (1) ethambutol, (2) isoniazid, (3) isoniazid plus ethambutol, (4) isoniazid plus rifampicin, (5) isonaiazid plus rifampic in plus ethambutol, or (6) no chemotherapy. The amount of tuberculous disease was scored and the spleen cultured in groups killed at intervals from 0--7 1/2 months after the end of chemotherapy. The regimens containing rifampicin were no more bactericidal during treatment than the corresponding regimens without rifampicin, but the onset of relapse after chemotherapy was delayed for at least 2 months following the rifampicin-containing regimens. Ethambutol alone did not protect guinea-pigs, nor did it influence the response to isoniazid or to isoniazid plus rifampicin. It was concluded that rifampicin may act selectively on a small proportion of the bacterial population and that it may be unnecessary to prescribe it for long periods in short course chemotherapy in man. Ethambutol does not appear likely to contribute to the sterilizing activity of short course regimens though it may prevent the emergence of drug resistance.

Experimental models to explain the high sterilizing activity of rifampin in the chemotherapy of tuberculosis.

Model systems were set up in vitro to explore the reasons why rifampin is a better sterilizing drug than isoniazid in short-course chemotherapy of tuberculosis. When the growth rate of Mycobacterium tuberculosis strain H37Rv was reduced uniformly by lowering the incubation temperature or the pH of the culture medium, the bactericidal activity of rifampin and isoniazid decreased to a similar extent. However, when a culture was maintained at 8 degrees C and incubated for daily periods of 1 or 6 h at 37 degrees C, rifampin killed more rapidly than isoniazid. Maintenance of control cultures without antimicrobials at 8 degrees C with or without periods at 37 degrees C, had little or no effect on their viability, ability to commence logarithmic growth at 37 degrees C, or to incorporate [14C]uridine. Old cultures left undisturbed or to which small additions of fresh culture medium were regularly added were killed more rapidly by rifampin than by isoniazid. These experiments supported the view that the special part of the bacterial population that is killed more rapidly by rifampin than by isoniazid during short-course chemotherapy consists of bacilli dormant much of the time but occasionally metabolising for short periods.

Turning intermittent regimens into daily regimens using blister-packs. An exploration in murine tuberculosis.

SETTING: Blisterpacks might be used to present low cost intermittent regimens while maintaining an easily remembered daily frequency of opening blisters, by alternating blisters containing 2 of the drugs of a 4-drug regimen with blisters containing the remaining 2 drugs. OBJECTIVE: The efficacy of the alternating regimens was examined in murine tuberculosis. DESIGN: 2 weeks after infection with Mycobacterium tuberculosis H37Rv, groups of mice were treated with rifampicin (R) 15 mg/kg, isoniazid (H) 25 mg/kg, pyrazinamide (Z) 300 mg/kg, ethambutol (E) 100 mg/kg three times weekly (RHZE3); RH/ZE, an alternating regimen of RH on days 1, 3 and 5 of the week and ZE on days 2, 4 and 6, RZ/HE or RE/HZ. RESULTS: Spleen and lung bacillary counts at 7 and 12 weeks indicated large differences in the efficacy of the regimens: RZ/HE > RE/HZ > RHZE3 > RH/ZE. Serum assays showed that Rifampicin (RMP) levels were much lower after HRZE and slightly lower after RZ, RE and RH than after R alone, whereas levels were similar when R was given before the remaining drugs; also, the absorption of Z was slightly increased by R. A second experiment used the same 4 regimens but gave R before other drugs. The organ colony forming units counts at 6 and 12 weeks were then similar. A third experiment examined continuation phase regimens of R3, R2, R2H2 and R2H6 given after daily RHZ treatment for 4 weeks. It found R2H2 only slightly superior to R2H6 and R3 much better than R2. CONCLUSION: 1. Alternating initial phase regimens were as effective as conventional intermittent regimens. 2. R3H6 might be an optimal continuation phase regimen for blisterpacks.