Search PubMed⌕ Search

Biomedical subjects

R K Martin

Publications and source records attributed to R K Martin.

At least 37 records · Page 2Linked to original sources
PubMed1991

Bundling--new products, new markets, low risk.

It has long been a marketing axiom that customers buy bundles of satisfaction, not products. It follows, then, that they'll respond to certain combinations of products and services--air conditioners with free installation, combinations of software packages, or season tickets with parking privileges. The difficulty is in devising the bundles that both appeal to consumers and give cost or demand enhancing benefits to the producer. Eppen, Hanson, and Martin argue that the best approach is to treat bundles not as marketing gimmicks but as new products. They offer seven guidelines for creating competitive bundles and a framework for implementing them.

Decision Making↗
PubMed1990

Several alleles of the multidrug-resistance gene are closely linked to chloroquine resistance in Plasmodium falciparum.

The lethal form of human malaria caused by Plasmodium falciparum is virtually uncontrollable in many areas because of the development of drug resistance, in particular chloroquine resistance (CQR). CQR is biologically similar to the multiple drug resistance phenotype (MDR) of mammalian tumour cells, as both involve expulsion of drug from the cell and both can be reversed by calcium channel antagonists. A homologue (pfmdr1) of the mammalian multidrug resistance gene has been implicated in CQR because it is amplified in some CQR isolates of P. falciparum as is an mdr gene in MDR tumour cells. We show here that the complete sequences of pfmdr1 genes from 2 CQ sensitive (CQS) P. falciparum isolates are identical. In 5 CQR isolates, 1-4 key nucleotide differences resulted in amino acid substitutions. On the basis of these substitutions, we have correctly predicted the CQS/CQR status of a further 34 out of 36 isolates. This is a paradox as CQR arises much less frequently than would be predicted if single point mutations were sufficient. We conclude that a mutated pfmdr1 gene is one of at least two mutated genes required for CQR.

Alleles↗
PubMed1988

Cystic fibrosis DNA markers in Alabama blacks.

DNA samples from unrelated Alabama blacks with no family history of cystic fibrosis (CF) were analyzed with DNA markers linked to cf. Allelic frequencies of genetic markers detected by probes pmetH, pmetD, XV2c, KM19, and pJ3.11 were compared to those of other populations. Allelic frequencies for pJ3.11, XV2c, and KM19 in Alabama blacks and previously studied Caucasian populations were similar. In contrast, the met locus allelic frequencies in Alabama blacks were markedly different from those in Caucasian populations.

Alabama↗
PubMed1988

Distribution and deposition of tritiated cortisol using phonophoresis.

Tritiated cortisol cream was coupled with light-microscopic autoradiography to histologically trace the distribution and deposition of a topical application of cortisol driven in by a therapeutic dose of ultrasound. Fifteen dogs were divided into four distinct groups: Group 1 consisted of two control dogs; Group 2, four dogs that received 10% radioactive cortisol and no ultrasound; Group 3, four dogs that received 5% radioactive cortisol plus ultrasound; and Group 4, five dogs that received 10% radioactive cortisol plus ultrasound. Although the cortisol applied to all dogs was limited to the epidermis, penetration occurred beyond the stratum corneum. The combination of 10% cortisol and ultrasound showed more penetration than 10% cortisol alone (p = .018), suggesting that ultrasound may be useful in the transdermal delivery of cortisol cream. The difference between the penetration of 5% and 10% cortisol when treated with ultrasound was only marginally significant (p = .062).

Administration, Topical↗
PubMed1987

Networking horizons.

Explore the source record for details and available documents.

Computer Communication Networks↗
PubMed1985

Cross-sectional thigh components: computerized tomographic assessment.

The purpose of this study was to examine the efficacy of the Picker Synerview Fourth Generation CT Scanner in assessing cross-sectional areas of muscle, bone, and subcutaneous fat of the thigh. A secondary purpose was to resolve individual muscle bellies using the CT scanner and to determine the effects of body composition in isolating those muscles. Both limbs of one cadaver were used to compare actual cross-sectional areas with the CT images. Each limb was dissected and photographed. Accuracy of repeated measurements was assessed using human volunteers. Absolute and percent error between the CT measurements and the measurements of the cross-sectional areas differed most at the bone. No differences were found between repeat scans. CT images and photographic measurements of individual muscles were generally quite similar, as assessed by absolute and percent error. The gracilis and sartorious were reasonably well defined in those individuals with more than 8% body fat. The results are discussed in terms of possible applications of the CT scanner in sports medicine research.

Adipose Tissue↗
PubMed1983

Digital processing of microradiographic and fluorochromic images from bone biopsy.

Bone biopsy is an essential technique for the diagnosis of metabolic bone disease and the skeletal response to remedial therapeutic maneuvers. Among many approaches in analyzing the biopsy specimen, the imaging technique offers the greatest potential. The objective of this paper is to describe the methodologies developed for digital processing of microradiographic and fluorochromic images from bone biopsy. This procedure requires a microscope with conventional and ultraviolet illuminations, a vidicon camera with three color filters, a general purpose image processing system with three image memories, a digital computer with some specially tailored software programs. A good specimen preparation from bone biopsy is a prerequisite in assuring the success of the method. The methodology for processing the microradiographs is based on a completely developed procedure of black and white image processing. Production run is in progress. The methodology for processing the fluorochromic images is based on true color imaging, although the procedure is still preliminary, early results obtained so far are promising.

Animals↗
PubMed1981

Bone loss in the beagle tibia: influence of age, weight, and sex.

In a cross-sectional study, 154 Beagles (79 males, 74 females) ranging in age from 14 to 187 months were measured for bone mineral, bone width, and mineral-to-width ratio on the distal shaft of the right tibia using a photon absorptiometer. The measurements were evaluated with regard to age, sex and body weight. The results indicate that males were heavier than females in body weight, with weight being reduced in the older animals of both sexes. When compared on an age basis, males had more mineral, a wider tibia, and a greater mineral-to-width ratio than females. The males and females reach their peak mineral, and mineral-to-width ratio at about 6 years of age and then decline. On a body weight basis, mineral, width and mineral-to-width ratio all increase with increasing body weight, with bone width being the least affected by changes in body weight. The values for females are less than those for males in all parameters with the greatest differences occurring at the greater weights. The only variance from these observations was the greater mineral-to-width ratio in the lighter females. It is concluded that, when examining cortical bone, the Beagle is a model of age-related osteopenia, and body weight is an important consideration when explaining changes in bone mineral.

Aging↗
PubMed1981

Load-carrying effects on the adult beagle tibia.

The response of the skeleton to carrying extra weight while exercising was studied in 30 young adult male beagles. Following 34 wk of a caged control period, 18 dogs carried lead-weighted jackets for 1 h and 15 min, 5 d/wk for 2 yr, on a carousel-type treadmill at 3.3 kph. During the next 23 wk, the load carried was gradually increased to 130% of the animal's body weight, and then maintained for 48 wk. The other 12 dogs served as controls. The dogs remained healthy and responded to exercise showing decreased skinfolds and body weight. All dogs showed increases in both tibial mineral content and width with time; but, the exercise group increased significantly more in mineral content than the controls. It is concluded that the gradual increase in bone mineral and width of the tibia is normal in the epiphyseal-closed skeleton of a young adult beagle. Also important is the fact that the intervention of exercise with added weight will increase tibial mineral content above these normal levels.

Animals↗
PubMed1981

Legg-Calvé-Perthes disease in dogs: a comparison to human Legg-Culvé-Perthes disease.

The femoral heads of 12 dogs with naturally occurring Legg-Calvé-Perthes disease were studied by light and electron microscopic techniques. In the early stages of the disease, the bony capital femoral epiphysis was necrotic, but the articular cartilage and growth plate cartilage were not affected. By the early stages of repair, the femoral head had collapsed. the articular cartilage was thickened and furrowed at the sites of collapse, and the chondrocytes appeared more metabolically active. Sites of bone resorption were associated with osteoclasts and macrophages. In some specimens there were areas of necrosis in the metaphysis which interrupted normal enchondral ossification in the growth plate. By the final stages of repair, the epiphysis was almost completely revascularized with the exception of the central proximal segment. In some areas, repair tissue had penetrated into the deeper layers of the articular cartilage. The flattening of the femoral head in Legg-Calvé-Perthes disease appears to be the result of several processes: mechanical collapse, asymmetric growth, and disturbed enchondral ossification at the growth plate.

Animals↗
PubMed1979

Concurrent exercise of dogs using carousel-type treadmill.

To exercise several animals at the same time, a carousel-type treadmill was constructed. Horizontal extensions secured to a motorized central shaft allow six dogs to be run concurrently. To counter the effect of centrifugal force, a rubberized banked running track was built. The track was also designed so that it can be hosed down for easy maintenance. During the past 2 yr, the treadmill has not required any maintenance, and only minimal attention has been necessary on the track.

Animals↗
PubMed1978

Influence of age and sex on the strength of bone-ligament junctions in knee joints of rats.

The bone-ligament junction strength of femur-medial collateral ligament-tibia complexes in rats was measured in situ at various ages during a two-year period. Male rats had a higher junction strength than female rats, a difference that became apparent when the animals were sixty days old and in male but not female animals subsequently paralleled the changes in body weight. However, on a bodyweight basis, the junctions were stronger in female than in male rats and this sex difference was evident at fifteen days old and persisted thereafter. Regression analysis between body weight and junction strength indicated that female rats had a significantly higher slope than males, which suggested that the sex differences were due to a hormonal factor or factors. Other measurements showed that elastic stiffness, failure energy, and collagen concentration in the ligament increased, whereas the water content of the ligament decreased with age. Most of these changes could be attriubted to the aging process and not the sex of the animal. It was concluded, however, that the strength of the insertion sites of ligaments on bones are responsive to the hormonal fluctuations that occur with aging.

Age Factors↗
PubMedDate not supplied

Innate resistance to new antimalarial drugs in Plasmodium falciparum from Nigeria.

The rapid dissemination of chloroquine-resistant Plasmodium falciparum in West Africa has been well documented and represents a significant health threat to autochthonous populations. The methodical development of alternative chemotherapeutic agents demands that dispensing new antimalarial drugs (mefloquine, halofantrine, and artemisinine [qinghaosu]) be closely monitored in order to protect their clinical utility. Indeed, mefloquine-resistant strains of P. falciparum have been reported. We present data from experiments in vitro on the innate resistance of P. falciparum isolates to mefloquine as well as a disturbing observation of transient resistance to artemisinine. The implications for the extended efficacy of these new antimalarial drugs are addressed.

Animals↗
PubMedDate not supplied

Head and neck injuries in college football: an eight-year analysis.

The present study documented head and neck injuries in a study group of 342 college football players at a single institution for a period of 8 years. All freshmen players were screened for evidence of: (1) past history of head and neck injuries, and (2) abnormalities of the cervical spine on physical examination and x-ray film. By recording all head injuries and those neck injuries with time loss, incidence rates and patterns of injury incurred in college competition were determined. A total of 175 head and neck injuries were sustained by 100 players over the 8 year period. Those players with abnormal findings on screening examination were twice as likely to have a head or neck injury at some point in their college careers as those players with a normal screening examination. The greater the degree of abnormality on freshman screening examination, the more severe the neck injury in college was likely to be. Twenty-nine percent of all players in the study group sustained a head or neck injury during their college careers. The probability of a subsequent head or neck injury escalated sharply following a single incident. The overall incidence of injury was found to have been dramatically reduced over the 8 years. Influential factors such as legislative rule changes, medical status of recruits, and general coaching philosophies are discussed with regard to injury reduction and prevention of head and neck injuries in college football.

Adult↗