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Biomedical subjects

A Howard

Publications and source records attributed to A Howard.

At least 19 recordsLinked to original sources

Transfusion practices and costs in dogs.

A geographically stratified sample of 25 small-animal practices administering at least six transfusions to dogs over the last 12 months was surveyed to determine how veterinarians obtain blood for transfusions, the direct costs of administering transfusions, and the impact of available blood on the management of critically ill dogs. The primary source of donor blood for each practice was a borrowed dog (12 practices) or in-house dogs kept on the premises (12 practices). Only one practice obtained blood from a nearby veterinary school. There was a wide variation in practices regarding testing for diseases and screening of donors. Thirty-six percent of practices surveyed did not screen dogs for infectious diseases or evaluate hematologic variables prior to blood donation. Twenty-four percent of the respondents evaluated the donors solely for the purposes of detecting microfilaria. The remaining 40% of the practices performed one or more of the tests generally recommended as part of a screening program for potential blood donors. The blood type of donors was determined in eight of the practices, whereas blood typing of recipients was not routinely performed. Ten of 25 practices performed blood crossmatches, but only one practice performed crossmatches in all cases. The distribution of direct costs per whole blood transfusion (500-ml unit) ranged from 25 to more than $300, with three fourths of the practices having costs less than $100. The higher-cost practices were those that maintained donors on the premises specifically for blood donation purposes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals

Molecular cloning and chromosomal assignment of human calbindin-D9k.

Human calbindin-D9k, the vitamin D-dependent calcium binding protein, has been cloned and sequenced following initial amplification of intestinal cDNA sequences by the polymerase chain reaction using mixed oligonucleotide primers. The derived amino acid sequence of 79 residues has a calculated molecular weight of 9015 and is 89% homologous with the bovine and porcine sequences. Probing DNA from human-rodent somatic cell hybrids mapped human calbindin-D9k to chromosome Xp. A single abundant mRNA transcript was detectable in proximal small intestine but not in kidney, uterus or placenta.

Amino Acid Sequence

Plasma membrane calcium pump expression in human placenta and small intestine.

To identify the forms of the plasma membrane calcium pump present in tissues that transport calcium, cDNA from human placenta and proximal small intestine was amplified by the polymerase chain reaction using a pair of mixed primers based on all the known human and rat plasma membrane calcium pump sequences. Clones were identified from the two human forms HPMCA1 and HPMCA4, but no new sequences were found in either tissue. RNA blots probed with HPMCA1 showed two bands in both tissues; probing with HPMCA4 gave a single, larger species. In placenta, HPMCA4 was the more abundant form and similar expression was found in full-term and second-trimester placentas. In contrast, in the small intestine, HPMCA1 was more abundant, suggesting that calcium absorption is not associated with any one specific isoform in calcium transporting cells.

Amino Acid Sequence

Characterization of rat gastric inhibitory peptide cDNA.

Gastric inhibitory peptide (GIP) is a 42 amino acid gastrointestinal peptide which inhibits gastric acid secretion and stimulates pancreatic insulin secretion in the presence of glucose. Here we report the sequence of the cDNA encoding the rat GIP precursor. PreproGIP was 144 amino acids in length and comprised the GIP peptide itself, N- and C-terminal flanking peptides of 22 and 59 amino acids respectively and a typical hydrophobic signal peptide. The sequence indicated that GIP is released from its precursor by cleavage at single arginine residues. The C-terminal flanking peptide may have an important function since it was well conserved and contained a region of 16 amino acids with only a single, conservative replacement. Rat GIP mRNA was found in the duodenum and jejunum. Levels of GIP mRNA in the duodenum were increased twofold after a period of 2 days of starvation. There was no detectable expression of the GIP gene in other parts of the gastrointestinal tract or in other endocrine tissues. However, in pancreatic mRNA preparations, a larger mRNA was detected after low stringency hybridization. This could represent a further member of this gene family.

Amino Acid Sequence

Stimulation of intestinal basolateral membrane calcium-pump activity by recombinant synthetic calbindin-D9k and specific mutants.

Calcium transport by the Ca2(+)-pumping ATPase in rat duodenal basolateral-enriched membrane vesicles was stimulated by synthetic calbindin-D9k in a similar fashion to the purified natural protein. In order to elucidate the mechanism of this effect, various synthetic mutant proteins were studied. Proteins with modifications to the N-terminal Ca2(+)-binding domain, or to a cluster of negatively-charged surface residues had altered Ca2(+)-binding but these changes did not affect the stimulation of vesicular Ca2+ transport. It appears that these domains are not essential for the interaction between calbindin-D9k and the intestinal basolateral Ca2(+)-pump.

Animals

Selection of appropriate exercise regimens for weight reduction during VLCD and maintenance.

Body composition, resting metabolic rate (RMR) and physical work capacity (aerobic capacity) were measured in four groups of 10 overweight women during 8 weeks of VLCD (405 kcal/day (42 g protein] followed by 8 weeks of 1500 kcal/day maintenance with two additional non dieting groups as controls. Five groups, i.e. two control groups plus three dieting groups, undertook exercise in bicycle ergometry (aerobic) or isotonic resistance or 8 week ergometry followed by 8 week resistance. Weight loss and body composition patterns were similar in diet and diet and exercise groups but efficiency of residual FFM in isotonic resistance groups improved significantly (P less than 0.05). Strength gains/kg body weight significantly improved (P less than 0.05) in the isotonic and dieting group. We conclude that exercise with VLCD is beneficial particularly isotonic resistance training, in improving muscular efficiency and RMR/lean.

Adult

Restoration to normal body composition by VLCD: a comparison of post obese and lean subjects questions BMI 25 as diet limit.

Body composition was assessed in naturally lean female subjects who never had need to diet. At BMI 21-22 their body weight distribution of 75 per cent FFM and 25 per cent fat was compared with subjects who had dieted below BMI 25 by various conventional self-selected diets; subjects who had dieted to BMI 21-22 by VLCD and subjects who were dieting with VLCD but were still above BMI 25. These body composition studies support values of BMI 22-22 as a better estimate of desirable weight in women than BMI 25. At BMI 21-22 the distribution of body weight between fat and FFM of post VLCD dieters matches that of normal lean women.

Body Composition

Rapid weight loss and lean tissue: evidence for comparable body composition and metabolic rate in differing rates of weight loss.

In assessing the desirability of very low calorie diets (VLCD) it is important to assess whether the additional calorie deprivation associated with a VLCD is within the range of physiological adaptation of normal people: specifically that the overweight person will return to normality in terms of body composition and metabolic rate. Comparison of fat free mass (FFM) and resting metabolic rate (RMR) change was made between two groups of dieting female subjects, whose weight loss was 1.9 kg/week (group A) and 1.1 kg/week (group B) over 8 weeks of diet. Body composition studies showed an equivalent FFM/Wt loss of 0.42 and 0.44 in the high and low weight loss groups respectively. As expected from the greater loss of weight, resting metabolic rate fell further in group A, but the RMR/FFM ratio remained the same (group A 21.3; group B 22.1). There is no evidence to suggest that the rate of weight loss achieved by VLCD is associated with any detriment to body composition or metabolic rate.

Basal Metabolism

Formulation change in VLCD in response to DHSS recommendations: comparative evaluation.

Response to recommendations of the Committee on Medical Aspects of Food Policy prompted reformulation of the 330 kcal Cambridge diet to 405 kcal per day with 42 g protein. Developmental trials demonstrated that clinical performance of VLCD formulations at comparable calorie levels could not be assumed. Studies using the formulation commercially produced as Cambridge diet extra with female subjects showed no significant difference in weight losses between the original and the new diet products over 2 or 8 week study periods. The percentage of body weight represented by FFM rose in the 8-week trial by 5 per cent in each group. Blood analyses were carried out before and after 8 weeks dieting with the 405 kcal formula. All parameters remained in the normal range, except iron, which was slightly below normal prior to the trial and rose into the normal range by week 8. These findings compared favourably with previous blood profiles of subjects using the 330 kcal formula. Modifications of the formula which increased the protein and calorie content to 42 g and 405 kcal respectively did not significantly alter the efficacy and safety of the product.

Body Composition

Site-directed antibodies for probing the structure and biogenesis of phosphatidylinositol glycan-linked membrane proteins: application to placental alkaline phosphatase.

An immunological approach to the study of the structure and biogenesis of the phosphatidylinositol glycan (PI-G) membrane anchor at the carboxyl terminus of human placental alkaline phosphatase (PLAP) is described. Based on the protein sequence predicted from full length PLAP cDNA, two epitopes were chosen in the region of the carboxyl terminus for the production of site-directed antibodies. The exo site represents the last nine residues of preproPLAP, (res. 505-513), which is part of the sequence that is expected to be cleaved from the nascent protein during processing and addition of the PI-G tail. A second site, the endo sequence, was selected close to the expected carboxyl terminus in mature PI-G-tailed PLAP (res. 474-484 of proPLAP). The two peptides were synthesized, polyclonal antibodies to the conjugated peptides were prepared, and the antisera were characterized. Analytical methods for both synthetic peptides and proteins are presented. Preliminary applications to the isolation and characterization of the PI-G-linked carboxyl terminus of mature PLAP and to the characterization of nascent PLAP are described. The application of both carboxyl terminal-directed antibodies, and a third antibody directed to the amino terminus of mature PLAP, in studies employing mutant forms of PLAP and to the PI-G tailing process itself are discussed. The immunological approach used here for PLAP should be applicable generally to the study of other PI-G-tailed proteins.

Alkaline Phosphatase

The gait of pacers. 1: kinematics of the racing stride.

Standardbred pacers have been studied under race conditions to describe the gait of the pacer, and to determine relationships between stage of the race, finish order and selected gait kinematics. Overlap increased with the stage of the race while pacing speed decreased marginally for low order pacers and increased for high order finishers. High order finishing pacers appear to have greater stance and stride lengths than do low order finishers. Pacers could be separated into low order and high order groups on the basis of their movement patterns. High order pacers exhibited greater ranges of limb motion than did low order finishers.

Animals

The gait of pacers. 2: factors influencing pacing speed.

Standardbred pacers were studied at four different nominated speeds and selected gait kinematics were analysed to determine factors which contribute to pacing speed. A deterministic model is proposed in which pacing speed is a function of stride length and stride timing variables. Stance length and suspension time remained relatively constant over the different pacing speeds. Variables which discriminated best between pacing speeds were suspension length and overlap time. At near maximal speed, the pacers increased speeds with increased stride length. This was attributed to an increased suspension length with little difference in suspension times. A 22 per cent increase in pacing speed resulted in a 13 per cent increase in stride length, 26 per cent increase in suspension distance, 8 per cent increase in stride frequency, 35 per cent and 16 per cent increases in advanced placement and completion times and a 23 per cent decrease in the period of overlap.

Animals

Clozapine-induced agranulocytosis: non-cross-reactivity with other psychotropic drugs.

Clozapine, an atypical neuroleptic with unique clinical and preclinical properties, represents a potentially valuable addition to the psychopharmacopeia. Its development and use have been limited by its higher frequency, compared with other pharmacologic treatments, of the potentially fatal side effect of agranulocytosis. This article describes the natural history of five cases of agranulocytosis that occurred in the course of clozapine treatment. The cases were generally uniform as to onset, recovery, and hematologic features. No patient had hematologic reactions to treatment with psychotropic agents before or after clozapine treatment. These findings, along with other work in progress, suggest that clozapine's granulocytoxic effects are produced by a highly specific immune-mediated mechanism.

Adult

Structural studies of Rubisco from tobacco.

An electron density map of ribulose 1,5-bisphosphate carboxylase-oxygenase (Rubisco) from tobacco (Nicotiana tabacum) has been obtained by X-ray crystallography at a nominal resolution of 0.34 nm. Phases were determined by multiple isomorphous replacement with three heavy atom derivatives and then refined by solvent flattening. Rubisco is barrel-shaped, and has (422) symmetry. The fourfold axis runs down an open central channel, concentric with the barrel. The molecule measures 10.5 nm along the fourfold axis, and has a diameter of 13 nm perpendicular to the fourfold axis at the widest point. The diameter of the central channel is 2.8 nm at the centre of the molecule, and 0.6 nm at its narrowest constriction. Portions of the polypeptide backbone of the promoter have been traced and some 127 residues have been assigned to 14 alpha-helices. The amino acid sequences of Rubisco from Rhodospirillum rubrum and from the large subunit of tobacco are sufficiently similar to suggest that the two chains are folded in the same general way.

Models, Molecular

Psychological consequences of majority-minority status: a questionnaire study of two high schools.

A questionnaire survey of high school students investigated the psychological phenomena associated with teenagers' membership in majority and minority groups. In the majority group, the socioeconomic status of parents was consonant with that of the high school; in the minority group, the status was dissonant with that of the school. The psychological impact of attending high schools that were consonant or dissonant with the student's family background was examined. The results are discussed in terms of the students' personal adjustments: views of their parents; and political, social, and personal attitudes and values. Minority teenagers were found to be more oriented to the home (especially to the mother) and to scholastic and future achievement, whereas majority teenagers were more oriented to their school peer group. Gender differences were also examined.

Adaptation, Psychological