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Biomedical subjects

I Schmidt

Publications and source records attributed to I Schmidt.

At least 19 recordsLinked to original sources
PubMed1992

An expression vector system providing plasmid stability and conditional suicide of plasmid-containing cells.

A cloning vector system was constructed on the basis of the pBR322 derivative pEG1 by introducing the whole parB locus of plasmid R1 cloned behind the promoter of the alkaline phosphatase gene (phoA) of Escherichia coli. The parB locus in combination with the phoA promoter ensures both (i) plasmid stabilization due to the post-segregational killing of plasmid-free cells during growth and (ii) killing of the cells induced by the potential environmental signal phosphate limitation. This vector, therefore, appears to be a model system for increasing the stability of recombinant plasmids and for decreasing the potential risks in the application of recombinant bacteria in industrial fermentations.

Alkaline Phosphatase↗
PubMed1992

Circadian changes of brown adipose tissue thermogenesis in juvenile rats.

The aim of this study was to determine whether the circadian cycle of core temperature (Tc) and oxygen consumption (VO2) in juvenile rats is correlated with changes in the thermogenic activity of brown adipose tissue (BAT). Nine-day-old rat pups derived from two colonies with 12:12 h light-dark cycles 180 degrees out of phase were artificially reared in continuous light for 12-48 h while Tc and VO2 were recorded. For measurement of GDP binding half the pups from each colony were killed during the maximum phase of their circadian Tc cycle and the other half during the minimum phase. During the maximum phase (0.5-2 h after lights-off in the colony of origin), when Tc was 36.1 +/- 0.1 degrees C, GDP binding (pmol/mg protein) was 575 +/- 31 (n = 19). During the minimum phase (0.5-2 h after lights-on), when Tc was 32.9 +/- 0.5 degrees C, GDP binding was 361 +/- 47 (n = 19). Moreover, the correlations between Tc, VO2, and GDP binding determined during the maximum plateau of the circadian cycle differ substantially from those determined during the minimum phase. Consequently, developmental studies of thermoregulation and BAT activity in suckling pups are seriously compromised if circadian phase is neglected.

Adipose Tissue, Brown↗
PubMed1990

Defective thermoregulatory thermogenesis does not cause onset of obesity in Zucker rats.

To test whether or not the onset of obesity in fatty (fa/fa) Zucker rats is caused by decreased thermoregulatory thermogenesis, pups were artificially reared above their lower critical temperature from 3 or 4 days of age. Littermates were continuously fed identical amounts of synthetic rat milk while body temperature (Tc) and oxygen consumption rate (VO2) were continuously recorded. When the daily mean Tc of all pups was held greater than 37 degrees C, neither Tc nor VO2 differed between fa/fa and genetically lean (Fa/-) pups during the first 2 wk of life. Tc and VO2 were significantly elevated in Fa/- pups during the third postnatal week. At both 16 and 21 days of age, fa/fa pups were identified by their low Tc during a brief cold exposure. Body fat and fat-free dry mass of fa/fa and Fa/- littermates differed at 21 but not at 16 days of age. The excess energy deposited as fat was partly derived from decreased nonthermoregulatory energy expenditure and decreased synthesis of lean body mass. Calculations support the speculation that a greater extraction of energy from the synthetic diet additionally supports the excess fat deposition. Decreased thermoregulatory thermogenesis and excess fat storage appear to be secondary and independent consequences of the primary genetic lesion.

Animals↗
PubMed1990

Development of circadian cycle of core temperature in juvenile rats.

To find out whether or not juvenile rats can sustain circadian rhythms of core temperature (Tc) in the absence of diurnal cues, we continuously recorded Tc for 12 days in isolated pups artificially reared in continuous dim light. Possible effects of uncontrolled environmental 24-h cycles were excluded by simultaneously studying pups born on the same day to two mothers entrained to 12:12 h light-dark cycles 180 degrees out of phase. Age-dependent changes were discriminated from the effects of sustained isolation by comparing Tc records between pups isolated from 10 or from 4 days of age (late- or early-isolated pups). Both groups of pups showed Tc cycles in phase with the light cycle in the colony of origin and with highest amplitudes from 10 to 13 days of age. Tc cycles with a period length close to 24 h could be seen through the 12th day of artificial rearing for early-isolated pups but only until the 6th day for late-isolated pups. In the third postnatal week the rhythm faded gradually. Self-sustained circadian Tc rhythms observed in isolated 1- to 2-wk-old pups demonstrate a functional endogenous clock in the juvenile rat.

Animal Husbandry↗
PubMed1989

Endogenous 24-hour cycle of core temperature and oxygen consumption in week-old Zucker rat pups.

Experiments were designed to test whether or not the 24-h core temperature fluctuations in week-old rat pups are of endogenous origin. Lean (Fa/-) Zucker rat pups born on the same day to mothers maintained in two different colonies with light/dark cycles 12 h out of phase with each other were mother-reared through the first 3-4 days of life and then artificially reared simultaneously in constant dim light. Continuous, automatic measurement of core temperature and oxygen consumption during artificial rearing showed clear 24-h rhythms in 5- to 8-day-old pups. Each rhythm reached a daily minimum at a time corresponding to the beginning of the light period in the colony of origin. The amplitude of these rhythms did not diminish during artificial rearing, nor did the phase difference between the rhythms of pups originating in the two colonies systematically change. The persistent 12-h phase differences between these two groups of pups prove that the observed rhythms are not caused by exogenous stimuli. We conclude that the rat pup possesses an endogenous time-keeping mechanism that permits the expression of overt rhythmicity at the age of 1 week.

Animals↗
PubMed1989

[Kidney function in the course of compensatory hypertrophy following unilateral nephrectomy in the Wistar rat].

Unilateral nephrectomy was performed in 109 male Wistar rats, 35 animals served as controls. Determinations of glomerular filtration rate (GFR) using slope clearance of 99mTc-DTPA and of tubular function using an orally water-loading test were made. The tests were performed 2 and 5 days as well as 2, 4, 5 and 6 weeks after nephrectomy. In all examinations the GFR was more than 50% of the level of two-kidney control animals. Fractional maximum diuresis was increased in the first 2 examinations after nephrectomy from 8.9 +/- 2.1 to 15.4 +/- 4.2% of the GFR and fractional clearance of osmotically free water from 6.8 +/- 1.9 to 10.9 +/- 3.5%. In the fourth and sixth week the proximal tubular reabsorption was increased and the glomerulo-tubular balance had been recovered. However, the minimal urine osmolarity was increased to 107.8 +/- 17.7 mmol/l and the osmotic load of the nephrons remained elevated. Possible clinical implications of the results are discussed.

Animals↗
PubMed1987

Nucleotide sequence of the gene encoding the surface projection glycoprotein of coronavirus MHV-JHM.

Sequences encoding the surface projection glycoprotein of the coronavirus, murine hepatitis virus (MHV), strain JHM, have been cloned into pAT153 using cDNA produced by priming with specific oligonucleotides on infected cell RNA. The regions of three clones pJMS1010, pJS112 and pJS92, which together encompass the surface protein gene have been sequenced by the chain termination method. The sequence of the primary translation product, deduced from the DNA sequence, predicts a polypeptide of 1,235 amino acids with a molecular weight of 136,600. This polypeptide displays the features characteristic of a group 1 membrane protein; an amino-terminal signal sequence and carboxy-terminal membrane and cytoplasmic domains. There are 21 potential glycosylation sites in the polypeptide and a cysteine-rich region in the vicinity of the transmembrane domain. During maturation proteolytic processing of the polypeptide occurs and at positions 624 to 628 the sequence Arg-Arg-Ala-Arg-Arg is found, which is similar to a number of basic sequences involved in the cleavage of enveloped RNA virus glycoproteins. The fusogenic properties of the MHV surface protein do not appear to correlate with a strongly hydrophobic region at the putative amino terminus of the carboxy-terminal cleavage product.

Amino Acid Sequence↗
PubMed1987

Thermoregulation and diurnal rhythms in 1-week-old rat pups.

This paper reviews the ontogeny of thermoregulation and diurnal rhythmicity in rats. Additionally, original data are presented that indicate the emergence of an endogenous circadian core temperature rhythm during the first postnatal week. Despite neurological immaturity, newborn rats display autonomic and behavioral thermoregulatory responses within 24 h of birth. Their "biological clock" is already running before birth. The thermal environment of pups changes cyclically owing to diurnal variations in maternal behavior, but the core temperatures of 1-week-old pups huddling in the absence of the dam also show marked diurnal fluctuations. Five- to 8-day-old lean Zucker rat pups artificially reared in the absence of 24-h cycles of ambient temperature and food intake show diurnal changes in core temperature similar to those in huddling mother-reared pups. Diurnal core temperature changes, evident only when regulatory effectors are not overwhelmed, are one of the first self-maintained diurnal rhythms to appear. Because thermoregulation and circadian rhythmicity both appear before maturation of the neural networks believed to be critical for their control in adult animals, studying the immature rat might increase our understanding of the control of these processes in the more complex mature central nervous system.

Aging↗
PubMed1986

Cathepsin S. The cysteine proteinase from bovine lymphoid tissue is distinct from cathepsin L (EC 3.4.22.15).

Cathepsin S was purified from bovine spleen by acid autolysis, (NH4)2SO4 fractionation and chromatography on CM-Sephadex C-50, CM-cellulose and activated-thiol-Sepharose. Cathepsin L was isolated from lysosomal fractions of rat liver, rat kidney and bovine liver. Generally, cathepsin L was bound tightly to CM-Sephadex C-50. Preparations of cathepsin L from rat liver, rat kidney and bovine liver were shown to have kinetic constants for the substrate benzyloxycarbonyl-Phe-Arg-7-(4-methyl)coumarylamide in the same range (Km 2-3 microM). Benzyloxycarbonyl-Phe-Phe-diazomethane proved to be a sensitive irreversible inhibitor of cathepsin L from different species. Cathepsin S differed in all these characteristics from cathepsin L. A polyclonal antibody to cathepsin L from rat reacted with bovine cathepsin L but not with bovine cathepsin S.

Animals↗
PubMed1986

[Dyskinetic syndrome following the use of metoclopramide].

The relation to the wide use of metoclopramide side effects are rare. These concern the extrapyramidal-motor system among others in form of dyskinetic syndrome. At the instance of a 15-year-old boy the dramatic course with cramp-like increases of the muscle tonus and compulsive movements in head and shoulder region are described. The knowledge of these medicament-induced symptoms is of differential-diagnostic importance to avoid false diagnose and to act with a definite aim. In easier forms of a dyskinetic syndrome suffices the discontinuation of the metoclopramide medication, in more severe cases proves the use of antiparkinsonian agents.

Adolescent↗
PubMed1986

Detection of antibodies to HTLV-III in commercially available immunoglobulin preparations.

Samples of 96 polyvalent and virus-specific immunoglobulin batches commercially available in West-Germany were tested by enzyme-linked immunoassay and immunoblot for the presence of anti-HTLV-III antibodies. 37% of the polyvalent and 87% of the virus-specific batches were positive. It was concluded that these preparations are still safe and because of their reportedly low titer neutralizing antibodies possibly beneficial in certain cases, such as newborns of HTLV-III positive mothers or after accidental exposure to infectious material in clinics or laboratories.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Cold-rearing normalizes capacity for norepinephrine-stimulated thermogenesis but not body temperature in 16-day-old fatty Zucker rats.

The effects of a lowered rearing temperature on body weight, core temperature (Tc) and norepinephrine(NE)-stimulated thermogenesis were investigated in 16- to 17-day-old Zucker rat pups. 16-day-old fatty pups were significantly heavier (9%) than lean littermates in litters reared at 18 degrees C ("cold-reared") but not in litters reared at 25 degrees C ("normally-reared"). After 2 h isolation at 25 degrees C, Tc of lean pups was slightly higher (37.1 degrees C) in cold-reared litters than in normally-reared litters (36.4 degrees C), while fatty pups reared at either temperature were severely hypothermic (Tc = 33 - 34 degrees C). At an ambient temperature of 25 degrees C Tc in fatty and lean cold-reared pups increased to 39.5 degrees C after subcutaneous injection of 800 micrograms/kg NE. Normally-reared lean pups reached the same peak Tc after NE injection, while their fatty littermates reached a significantly lower peak Tc of 38.4 degrees C. The hypothermia associated with the onset of excess fat deposition in suckling fatty Zucker rats is not caused by a reduced capacity for NE-stimulated thermogenesis.

Adipose Tissue, Brown↗
PubMed1986

Diurnal cycle of core temperature in huddling, week-old rat pups.

Lean Zucker rat pups were reared at 25 degrees C on four staggered 12:12 light:dark cycles with lights on at 0100, 0700, 1300 or 1900 hr. Core temperature (Tc) of 5- to 8-day-old pups was measured repeatedly at the rearing temperature of 25 degrees C between 0700 and 1900 hr using a procedure that minimally interfered with spontaneous nursing cycles and huddling of the pups. Tc of litters measured 30 to 60 min after the mother spontaneously left the nest was low and variable (32.2-35.4 degrees C) during the first few hours after lights-on, but was uniformly high and much less variable (35.5-36.5 degrees C) around the time of lights-off. Pup Tc was phase-advanced to the nocturnal elevation of maternal Tc, and lagged several hours behind the diurnal elevation of nursing activity. Cyclic variations in Tc of pups huddling in the nest thus reflect a diurnal rhythm in the ability and/or drive for body temperature defense that is independent of heat derived from the mother during nursing.

Animals↗
PubMed1986

Are there species differences amongst the lysosomal cysteine proteinases?

Kinetic constants for the hydrolysis of synthetic substrates by cathepsin B, cathepsin L or cathepsin H show only small variations between various species. The species variants purified from human, beef and rabbit reacted with antisera raised against the enzymes from rat. With regard to these criteria we could show that cathepsin I from rabbit lung is a species variant of cathepsin H, whereas cathepsin S is a separate enzyme from cathepsin L.

Animals↗