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Biomedical subjects

D G Johnson

Publications and source records attributed to D G Johnson.

At least 163 records · Page 9Linked to original sources
PubMed1983

Effects of moisture content of complete diets on feed intake and milk production by cows.

In two trials, 47 and 54 Holstein cows were fed diets containing ensiled forages, ensiled and dry forages, or diets of different moisture contents. In trial 1, diets were fed during a preliminary dry period, early lactation, late lactation, a second dry period, and a second early lactation. In trial 2, four diets identical except for moisture content (78, 64, 52, and 40% dry matter) were fed for the first 200 days of lactation. Substitution of dry hay for alfalfa silage increased dry matter intake during the first early lactation, whereas partial substitution of corn silage with straw did not affect intake during dry periods. Dry matter intake increased linearly as dry matter content of diet increased in trial 2. Neither milk production nor body weight were affected by treatment in either trial. Percentage total solids increased linearly as dry matter content of diet decreased in trial 2. Volatile fatty acids differed slightly, but no trends were consistent. No differences of daily chewing time were observed. From these trials, diets of less than 60 to 65% dry matter may reduce intake by lactating dairy cows.

Animals↗
PubMed1982

Hyperglycemia of diabetic rats decreased by a glucagon receptor antagonist.

The glucagon analog [l-N alpha-trinitrophenylhistidine, 12-homoarginine]-glucagon (THG) was examined for its ability to lower blood glucose concentrations in rats made diabetic with streptozotocin. In vitro, THG is a potent antagonist of glucagon activation of the hepatic adenylate cyclase assay system. Intravenous bolus injections of THG caused rapid decreases (20 to 35 percent) of short duration in blood glucose. Continuous infusion of low concentrations of the inhibitor led to larger sustained decreases in blood glucose (30 to 65 percent). These studies demonstrate that a glucagon receptor antagonist can substantially reduce blood glucose levels in diabetic animals without addition of exogenous insulin.

Animals↗
PubMed1982

Insertion of a small central venous catheter in neonates and young infants.

Total parenteral nutrition (TPN) administered through a central venous catheter in low-birthweight neonates and infants has been complicated by mechanical catheter malfunctions and catheter-associated infections. A retrospective survey of catheter complications 66 infants with 90 pediatric Broviac (1.3 mm o.d.) and large-diameter (French size 3, 4, and 5) Silastic catheters revealed 17 mechanical malfunctions (27%) and 16 cases (26%) of catheter infections. The current study presents our experience using 58 small-diameter (0.635 mm o.d.) Silastic catheters for TPN in 53 neonates and infants. There were 13 episodes (22%) of mechanical problems such as accidental dislodgement, occlusion of the catheter, and perforation of the tubing. Only four cases (7%) of catheter-associated sepsis occurred, a significant reduction (p = 0.008) in this serious problem compared to the previous large catheter study. We have compared clinical features of both large- and small-diameter catheters and suggest specific guidelines for their use. The small-diameter Silastic catheter is safe, easily inserted, and effective in the critically ill, low-birthweight neonate and in young infants weighing less than 6 kg. The pediatric Broviac catheter is recommended for administration of long-term or home TPN to infants and children greater than 6 kg. These catheters are useful for multiple purposes such as blood drawing, chemotherapy, and nutritional support while the small catheter is not as versatile.

Calibration↗
PubMed1982

Splanchnic vasoconstriction in heat-stressed men: role of renin-angiotensin system.

We conducted a two-part study to determine whether the renin-angiotensin system contributes to the rise in splanchnic vascular resistance (SVR) during heat stress (rectal temperature was raised 1 degree C). In experiment 1 (control) seven men on a normal salt diet were directly heated (water-perfused suits) for 40-50 min. Arterial pressure (85 Torr) was unchanged; plasma renin activity (PRA) rose from 102 to 239 ng angiotensin I.100 ml-1.3 h-1; and SVR increased 73% (from 63 to 109 units). Experiment 2 was a repetition of experiment 1 on the same subjects, except that propranolol (10 mg iv) was given at the onset of heating to block renin release. Propranolol attenuated the rise in heart rate and reduced mean arterial pressure from 82 to 72 Torr; it blocked the rise in PRA with heating in two subjects, reduced it in three, but increased it in two. Although changes in SVR paralleled those in PRA in three subjects, SVR still rose 60% (from 58 to 99 units) after PRA rise was blocked. In both experiments, plasma norepinephrine concentration rose indicating increased sympathetic nervous activity. During mild heat stress, increased PRA is not a major factor in the increase of SVR.

Adult↗
PubMed1982

Practice patterns of black physicians: results of a survey of Howard University College of Medicine alumni.

Over 600 Howard University medical alumni of seven representative classes graduating from 1955 to 1975 were surveyed by questionnaire in 1975 and 1976. Replies of the 252 black respondents confirm that these graduates are providing substantial care to blacks, the economically disadvantaged, and residents of the inner city. Survey findings reaffirm the necessity to train more black physicians and to provide data on current and future practice patterns. Comparisons are made between the practice patterns of earlier (1955 to 1970) and later (1973 to 1975) black graduates. A general bibliography of publications relevant to the practice patterns of black physicians is included.

Black or African American↗
PubMed1981

Causes of morbidity and mortality in severe pediatric trauma.

In a two-year period, we studied 160 patients with multiple trauma (injury to at least two body areas) and graded severity of neurologic injury according to the Glasgow Coma Scale. Injuries to other body areas were categorized by the Modified Injury Severity Scale. Neurologic injury was present in nearly 80% and constituted the most severe injury in 60%. Chest (40%) and extremity (30%) injuries were next most frequently encountered. Overall mortality was 13.8%, with 11.3% disability and 74.3% of patients achieving good recovery. There was some degree of neurologic injury in all patients who died or were disabled. Among all patients with head injuries (126), mortality was 16%, vs 6% in those without head injury (34). Other deaths were caused by chest (9%) or abdominal (14.5%) injuries.

Accidents, Home↗
PubMed1981

Pattern of immunoreactive glucagon in portal, arterial and peripheral plasma before and after removal of glucagonoma.

Gel fractionation of portal, arterial and peripheral plasma glucagon levels was performed before and after the successful removal of a glucagonoma. A 47 year old woman had symptoms of dermatitis, weight loss, anemia and diabetes mellitus over a 16 year period. Removal of the alpha-cell tumor corrected all of her symptoms. Gel filtration of portal, arterial and peripheral blood showed two peaks of glucagon radioimmunoassay activity, a higher molecular weight glucagon with a molecular weight of 9,000 and a 3,500 dalton glucagon. Five minutes after tumor removal, the higher molecular weight glucagon had disappeared completely from the arterial and peripheral blood but not from the portal vein.

Adenoma, Islet Cell↗
PubMed1981

Surgical selection of infants with gastroesophageal reflux.

Gastroesophageal reflux (GER) can produce debilitating and even fatal disease in infants and children. GER is common in infancy, and most GER subsides with time or with postural and dietary therapy. Operation is justified only to control effectively by nonoperative methods. The clinical history and the patient's response to medical treatment remain the most important factors in our decision for or against operation. As in adults, esophagoscopy and esophageal biopsy are useful to document the presence of reflux in older children, but they seldom contribute to the decision for operation in infants. In our hands, gastric scintiscan has provided useful qualitative data on reflux-induced respiratory symptoms and quantitative data on gastric emptying. Esophageal pH monitoring is more quantitative for reflux evaluation and allows analysis and clinical correlations with reflux patterns. We have not used the reflux patterns to predict outcome or response to treatment in the individual patient. A prolonged average duration of reflux during sleep does appear to increase the probability that a patient with respiratory symptoms will respond to operative control of reflux. Our presently imprecise technique for patient selection, however, must not cause us to withhold operation from needy infants. For the infant who does not grow or who aspirates on a reflux board, or who requires prolonged hospitalization and for the preemie who aspirates at every extubation attempts or requires long-term nasojejunal feedings to prevent aspiration, we think antireflux surgery is appropriate, humane, and cost-effective. We see no excuse for persisting with ineffective management of a process that may result in stunting, chronic illness, persistent pain, esophageal scarring, or even respiratory death.

Esophageal Atresia↗
PubMed1981

Combined modality therapy with conservation of organ function in childhood genitourinary rhabdomyosarcoma.

Recent refinements in the multimodal therapy of childhood genitourinary rhabdomyosarcoma have produced striking improvements in long-term survival rates while still preserving pelvic organ function in the majority of cases. Three illustrative cases of childhood pelvic rhabdomyosarcoma are presented. Chemotherapy and surgical staging are employed in all 3 cases, with 2 of the cases requiring additional local tumor excision and intraurethral radiation for control of residual microscopic tumor. While long-term follow-up has not been achieved, all 3 patients have had their pelvic organs preserved and remain tumor-free in follow-up periods ranging from twelve to twenty-four months after the initial diagnosis.

Child, Preschool↗
PubMed1981

Postcibal gastroesophageal reflux in children.

The effect of eating on childhood gastroesophageal reflux (GER) is unclear. Twenty-eight asymptomatic children and 28 children with symptoms of GER were fed apple juice or milk-formula and observed for 3 hr postcibal. Distal esophageal pH was monitored continuously during this interval and used to quantitate the frequency and duration of GER. A period of frequent GER occurred for up to 2 hr after apple juice feedings in asymptomatic children, whereas symptomatic patients had frequent GER for longer periods. Compared to apple juice feedings, milk-formula feedings resulted in a decreased esophageal acidity for the first 2 hr. However, the type of feeding did not affect GER seen in asymptomatic children more than 2 hr postcibal. The frequency and duration of postcibal GER were not reduced by the upright position in either group. Effective medical treatment of symptomatic children did not eliminate the frequent GER within 2 hr of apple juice feedings, whereas the Nissen fundoplication usually eliminated all GER. The absence of GER episodes following apple juice correlated with the inability of most children to burp or vomit following antireflux surgery. Therefore, frequent GER for up to 2 hr after clear liquid meals is probably physiologic in children. The effective control of vomiting by medical or surgical therapy correlated best with a decrease in GER more than 2 hr postcibal.

Child, Preschool↗
PubMed1981

Gastroesophageal reflux in infants and children. Recognition and treatment.

Gastroesophageal reflux is common in infants and children and is associated with a broad spectrum of symptoms and disease. The majority of young patients with reflux can be managed nonoperatively because growth and time usually bring maturation of the antireflux mechanisms. We feel that operation is justified and indicated for the child with complications of reflux that are not reversed by a six-week medical trial, and children with stricture or infants with reflux-related apnea should have operation without delay. In our experience, analysis of the 24-hour esophageal pH tracing has proved most useful to correlate respiratory symptoms with reflux. The Nissen fundoplication is the most effective and the most reliable antireflux procedure, but it must be constructed loosely to minimize the side effects of dysphagia and gas bloating. Because the population at risk for reflux disease has approximately a 50 per cent incidence of significant associated medical problems, morbidity and mortality from some of these problems is inevitable. There should be little or no mortality associated with the antireflux operation itself.

Adolescent↗
PubMed1981

Protean manifestations of neonatal hyperinsulinism.

Endogenous hyperinsulinism is the leading cause of persistent hypoglycemia in children under one year of age. Classically, the symptoms of neonatal hypoglycemia have been referable to central nervous system dysfunction, with seizures described in nearly all patients. Our experience with eight neonates emphasizes the protean manifestations of this disease. One patient presented with a maternal history of diuretic use, and developed asymptomatic hyperinsulinism documented by provocative testing. The hyperinsulinism cleared after two weeks of medical therapy. This transient hyperinsulinism may have been secondary to use of a thiazide-type diuretic. A second patient presented, as a neonate, with a large abdominal mass but no seizure activity. Exploratory laparotomy revealed an 11 x 5 x 3 cm pancreatic tumor, which required splenectomy, 60% gastrectomy and duodenectomy for removal. Histologic examination demonstrated an insulin-secreting hamartoma. A third patient died suddenly without prior symptoms, and was found to have striking nesidioblastosis on pathologic examination. One infant presented with absence of the abdominal musculature (prune belly syndrome) and features of the Beck-with-Wiedeman syndrome, as well as profound hypoglycemia. Only three patients had seizures, and an additional patient had jitteriness. Pathologic diagnoses were: nesidioblastosis (n = 2); islet cell hyperplasia (n = 1); adenoma (n = 1); hamartoma (n = 1); transient hyperinsulinism (n = 1). One patient's pancreas showed areas of nesidioblastosis, islet cell hyperplasia, and a discrete adenoma in the region of the common bile duct. Careful diagnostic testing is essential in these patients, inasmuch as hypoglycemia is poorly tolerated by neonates and infants. Using the diagnostic algorithm presented here, all patients' endogenous hyperinsulinism was documented quickly and efficiently. Recognition of the broad spectrum of symptoms with which these patients may present is essential if serious neurologic sequelae are to be avoided.

Chlorthalidone↗
PubMed1981

Gynecomastia with ketoconazole.

Three of forty men developed bilateral gynecomastia upon ketoconazole treatment. Symptoms abated despite continued therapy. This appears to be a direct drug effect on breast tissue.

Adult↗